Intragastric device with expandable portions

ABSTRACT

Devices and methods for treating obesity are provided. More particularly, intragastric devices and methods of fabricating, deploying, inflating, monitoring, and retrieving the same are provided.

INCORPORATION BY REFERENCE TO RELATED APPLICATION

Any and all priority claims identified in the Application Data Sheet, orany correction thereto, are hereby incorporated by reference under 37CFR 1.57. This application is a continuation of U.S. application Ser.No. 15/335,256, filed Oct. 26, 2016, which claims the benefit of U.S.Provisional Application No. 62/268,389, filed Dec. 16, 2015. Each of theaforementioned applications is incorporated by reference herein in itsentirety, and each is hereby expressly made a part of thisspecification.

FIELD OF THE INVENTION

Devices and methods for treating obesity are provided. Moreparticularly, intragastric devices and methods of fabricating,deploying, inflating, monitoring, and retrieving the same are provided.

BACKGROUND OF THE INVENTION

Obesity is a major health problem in developed countries. Obesity putsyou at greater risk of developing high blood pressure, diabetes and manyother serious health problems. In the United States, the complicationsof being overweight or obese are estimated to affect nearly one in threeAmerican adults, with an annual medical cost of over $80 billion and,including indirect costs such as lost wages, a total annual economiccost of over $120 billion. Except for rare pathological conditions,weight gain is directly correlated to overeating.

Noninvasive methods for reducing weight include increasing metabolicactivity to burn calories and/or reducing caloric intake, either bymodifying behavior or with pharmacological intervention to reduce thedesire to eat. Other methods include surgery to reduce the stomach'svolume, banding to limit the size of the stoma, and intragastric devicesthat reduce the desire to eat by occupying space in the stomach.

Intragastric volume-occupying devices provide the patient a feeling ofsatiety after having eaten only small amounts of food. Thus, the caloricintake is diminished while the person is satisfied with a feeling offullness. Currently available volume-occupying devices have manyshortcomings. For example, complex gastric procedures are required toinsert some devices.

U.S. Pat. No. 4,133,315, the contents of which are incorporated hereinby reference in their entirety, discloses an apparatus for reducingobesity comprising an inflatable, elastomeric bag and tube combination.The bag can be inserted into the patient's stomach by swallowing. Theend of the attached tube distal to the bag remains in the patient'smouth. A second tube is snaked through the nasal cavity and into thepatient's mouth. The tube ends located in the patient's mouth areconnected to form a continuous tube for fluid communication through thepatient's nose to the bag. Alternatively, the bag can be implanted by agastric procedure. The bag is inflated through the tube to a desireddegree before the patient eats so that the desire for food is reduced.After the patient has eaten, the bag is deflated. The tube extends outof the patient's nose or abdominal cavity throughout the course oftreatment.

U.S. Pat. Nos. 5,259,399, 5,234,454 and 6,454,785, the contents of whichare incorporated herein by reference in their entirety, discloseintragastric volume-occupying devices for weight control that must beimplanted surgically.

U.S. Pat. Nos. 4,416,267, 4,485,805, 4,607,618, 4,694,827, 4,723,547,4,739,758, and 4,899,747 and European Patent No. 246,999, the contentsof which are incorporated herein by reference in their entirety, relateto intragastric, volume-occupying devices for weight control that can beinserted endoscopically. Of these, U.S. Pat. Nos. 4,416,267, 4,694,827,4,739,758 and 4,899,747, the contents of which are incorporated hereinby reference in their entirety relate to balloons whose surface iscontoured in a certain way to achieve a desired end. In U.S. Pat. Nos.4,416,267 and 4,694,827, the contents of which are incorporated hereinby reference in their entirety, the balloon is torus-shaped with aflared central opening to facilitate passage of solids and liquidsthrough the stomach cavity. The balloon of U.S. Pat. No. 4,694,827, thecontents of which are incorporated herein by reference in theirentirety, has a plurality of smooth-surfaced convex protrusions. Theprotrusions reduce the amount of surface area which contacts the stomachwall, thereby reducing the deleterious effects resulting from excessivecontact with the gastric mucosa. The protrusions also define channelsbetween the balloon and stomach wall through which solids and liquidsmay pass. The balloon of U.S. Pat. No. 4,739,758, the contents of whichare incorporated herein by reference in their entirety, has blisters onits periphery that prevent it from seating tightly against the cardia orpylorus.

The balloons of U.S. Pat. Nos. 4,899,747 and 4,694,827, the contents ofwhich are incorporated herein by reference in their entirety, areinserted by pushing the deflated balloon and releasably attached tubingdown a gastric tube. U.S. Pat. No. 4,723,547, the contents of which areincorporated herein by reference in their entirety discloses a speciallyadapted insertion catheter for positioning its balloon. In U.S. Pat. No.4,739,758, the contents of which are incorporated herein by reference intheir entirety, the filler tube effects insertion of the balloon. InU.S. Pat. No. 4,485,805, the contents of which are incorporated hereinby reference in their entirety, the balloon is inserted into a fingercot that is attached by string to the end of a conventional gastric tubethat is inserted down the patient's throat. The balloon of EuropeanPatent No. 246,999 is inserted using a gastroscope with integralforceps.

In U.S. Pat. Nos. 4,416,267, 4,485,805, 4,694,827, 4,739,758, and4,899,747 and European Patent No. 246,999, the contents of which areincorporated herein by reference in their entirety, the balloon isinflated with a fluid from a tube extending down from the patient'smouth. In these patents, the balloon also is provided with aself-sealing hole (U.S. Pat. No. 4,694,827, the contents of which areincorporated herein by reference in their entirety), injection site(U.S. Pat. Nos. 4,416,267 and 4,899,747, the contents of which areincorporated herein by reference in their entirety), self-sealing fillvalve (U.S. Pat. No. 4,485,805, the contents of which are incorporatedherein by reference in their entirety), self-closing valve (EuropeanPatent No. 246,999, the contents of which are incorporated herein byreference in their entirety) or duck-billed valve (U.S. Pat. No.4,739,758, the contents of which are incorporated herein by reference intheir entirety). U.S. Pat. No. 4,723,547, the contents of which areincorporated herein by reference in their entirety, uses an elongatedthick plug and the balloon is filled by inserting a needle attached toan air source through the plug.

U.S. Pat. No. 4,607,618, the contents of which are incorporated hereinby reference in their entirety, describes a collapsible appliance formedof semi-rigid skeleton members joined to form a collapsible hollowstructure. The appliance is not inflatable. It is endoscopicallyinserted into the stomach using an especially adapted bougie having anejector rod to release the collapsed appliance. Once released, theappliance returns to its greater relaxed size and shape.

U.S. Pat. No. 5,129,915, the contents of which are incorporated hereinby reference in their entirety, the contents of which are incorporatedherein by reference, relates to an intragastric balloon that is intendedto be swallowed and that inflates automatically under the effect oftemperature. Three ways that an intragastric balloon might be inflatedby a change in temperature are discussed. A composition comprising asolid acid and non-toxic carbonate or bicarbonate is separated fromwater by a coating of chocolate, cocoa paste or cocoa butter that meltsat body temperature. Alternatively, citric acid and an alkalinebicarbonate coated with non-toxic vegetable or animal fat melting atbody temperature and which placed in the presence of water, can producethe same result. Lastly, the solid acid and non-toxic carbonate orbicarbonate are isolated from water by an isolation pouch oflow-strength synthetic material which it will suffice to breakimmediately before swallowing the bladder. Breaking the isolationpouches causes the acid, carbonate or bicarbonate and water to mix andthe balloon to begin to expand immediately. A drawback of thermaltriggering of inflation is that it does not afford the degree of controland reproducibility of the timing of inflation that is desirable andnecessary in a safe self-inflating intragastric balloon.

SUMMARY OF THE INVENTION

A free-floating intragastric volume-occupying device that maintains itsvolume and/or internal pressure within a predetermined range over time,or which undergoes a predetermined adjustment in volume and/or internalpressure over time, is desirable. By maintaining a predetermined volumeand/or internal pressure, stresses on the device leading to a breach instructural integrity can be minimized, which prevents premature and/oruncontrolled deflation or other device failure. By undergoing apredetermined adjustment in volume and/or internal pressure over time, apreselected volume profile can be obtained to accommodate changes instomach size over the course of treatment with the device. The devicescan be self-inflating (also referred to as automatic inflating) orinflatable (also referred to as manually inflating via a tether).

Volume-occupying devices and methods for manufacturing, deploying,inflating, tracking, deflating and retrieving of such devices areprovided. The devices and methods of the preferred embodiments may beemployed for treating over weight and obese individuals. Methodsemploying the device of the preferred embodiments need not utilizeinvasive procedures, but rather the device may simply be swallowed by apatient, with or without a catheter attached. Once in the stomach of thepatient, the device is inflated with a preselected gas or mixture ofgases, to a preselected volume. The wall of the device is preselectedfor its particular gas diffusion properties. Once in the in vivoenvironment, the gas(es) within the device diffuse out through the wallof the device, and gases diffuse into the device from the in vivoenvironment. By preselecting the device wall and gas(es) initiallyemployed to inflate the device, taking into account diffusion propertiesof gases into the device from the in vivo environment, the volume and/orinternal pressure of the device can be maintained within a preselectedrange, or can follow a preselected profile of volume and/or pressurechanges. After a predetermined time period, the device can be removedusing endoscopic tools or will decrease in volume or deflate so as topass through the remainder of the patient's digestive tract.

Inflation may be achieved by use of a removable catheter that initiallyremains in fluid contact with the device after it has been swallowed bythe patient. Alternatively, inflation may be achieved by aself-inflation process, e.g., generation of gas in the device once itreaches the stomach by reaction of gas-generating components containedwithin the device upon swallowing, or by introduction of one or morecomponents in the gas generating process into the device by use of aremovable catheter.

The volume-occupying subcomponent of devices may be formed by injection,blow or rotational molding of a flexible, gas-impermeable, biocompatiblematerial, such as, for example, polyurethane, nylon or polyethyleneterephthalate. Materials that may be used to control the gaspermeability/impermeability of the volume-occupying subcomponentinclude, but are not limited to, silicon oxide (SiOx), gold or any noblemetal, saran, conformal coatings and the like, when it is desired toreduce permeability. To enhance gas-impermeable characteristics of thewall of the device, if desirable, the volume-occupying subcomponent maybe further coated with one or more gas-barrier compounds, or be formedof a Mylar polyester film coating or kelvalite, silver or aluminum as ametalized surface to provide a gas impermeable barrier.

In further embodiments, the device employs a delivery state in which thedevice is packaged such that the device may be swallowed while producingminimal discomfort to the patient. In a delivery state, the device maybe packaged into a capsule. Alternatively, the device may be coated witha material operable to confine the device and facilitate swallowing.Various techniques may also be employed to ease swallowing of the deviceincluding, for example, wetting, temperature treating, lubricating, andtreating with pharmaceuticals such as anesthetics.

In other embodiments, the devices may incorporate a tracking orvisualization component that enables physicians to determine thelocation and/or orientation of the device within the patient's body.Tracking subcomponents may include incorporating a barium stripe orgeometric shape into the wall of the volume-occupying subcomponent.Tracking and visualization, may also be achieved by incorporation of amicrochip, infrared LED tag, ultraviolet absorbing compounds,fluorescent or colored compounds and incorporation of metalized stripsand patterns into the volume-occupying subcomponent or othersubcomponents of the device. Such techniques may also be used to obtaincertain device specific information and specifications while the deviceremains inside the patient's body.

In a first aspect, an intragastric balloon is provided, comprising: avalve system configured for introducing an initial fill gas into theballoon in vivo; and a polymeric wall comprising one or more layers,wherein the polymeric wall is configured to have, under in vivoconditions, a permeability to CO₂ of more than 10 cc/m²/day, and whereinthe polymeric wall is configured such that, in vivo, the balloon isconfigured to gain in volume and in pressure during a useful life of theintragastric balloon when filled with an initial fill gas consistingessentially of a gas selected from the group consisting of argon,nitrogen, oxygen, carbon dioxide, hydrogen, and mixtures thereof.

In an embodiment of the first aspect, the initial fill gas consistsessentially of N₂.

In an embodiment of the first aspect, the initial fill gas consistsessentially of N₂ and CO₂.

In an embodiment of the first aspect, the initial fill gas consistsessentially of N₂ and O₂.

In an embodiment of the first aspect, the initial fill gas consistsessentially of N₂, O₂, and CO₂.

In an embodiment of the first aspect, the polymeric wall comprises a CO₂barrier material consisting of nylon/polyvinylidenechloride/polyethylene.

In an embodiment of the first aspect, the polymeric wall comprises anylon/polyethylene material and no additional CO₂ barrier material.

In an embodiment of the first aspect, the balloon is configured to gainfrom 5% to 300% in volume during the useful life.

In an embodiment of the first aspect, the balloon is configured to gainfrom 10% to 500% in pressure during the useful life.

In an embodiment of the first aspect, the useful life is at least 30days.

In a second aspect, a method is provided for inflating an intragastricballoon, comprising: providing an intragastric balloon comprising avalve system and a polymeric wall, wherein the polymeric wall comprisesone or more layers, and wherein the polymeric wall is configured tohave, under in vivo conditions, a permeability to CO₂ of more than 10cc/m²/day; introducing, in an in vivo intragastric environment, aninitial fill gas into the intragastric balloon through the valve systemto an initial volume and an initial pressure, wherein the initial fillgas consists essentially of a gas selected from the group consisting ofargon, nitrogen, oxygen, carbon dioxide, hydrogen, and mixtures thereof;and exposing the filled balloon to the in vivo intragastric environmentfor a useful life of the intragastric balloon, whereby the initial fillgas diffuses through the polymeric wall and into the in vivointragastric environment, and whereby gases in the in vivo intragastricenvironment diffuse into the balloon through the wall, whereby theintragastric balloon gains in volume and in pressure over the usefullife.

In an embodiment of the second aspect, the initial fill gas consistsessentially of N₂.

In an embodiment of the second aspect, the initial fill gas consistsessentially of N₂ and CO₂.

In an embodiment of the second aspect, N₂ is excess in concentration toCO₂ in the initial fill gas.

In an embodiment of the second aspect, the initial fill gas consistsessentially of N₂ and O₂.

In an embodiment of the second aspect, N₂ is excess in concentration toO₂ in the initial fill gas.

In an embodiment of the second aspect, the initial fill gas consistsessentially of N₂, O₂, and CO₂.

In an embodiment of the second aspect, N₂ is excess in concentration toO₂ and CO₂ combined in the initial fill gas.

In an embodiment of the second aspect, the polymeric wall comprises aCO₂ barrier material consisting of nylon/polyvinylidenechloride/polyethylene.

In an embodiment of the second aspect, the polymeric wall comprises anylon/polyethylene material and no additional CO₂ barrier material.

In an embodiment of the second aspect, the balloon gains from 5% to 300%in volume over the useful life.

In an embodiment of the second aspect, the balloon gains from 10% to500% in pressure over the useful life.

In an embodiment of the second aspect, the useful life is at least 30days.

In a third aspect, an intragastric balloon is provided, comprising: avalve system configured for introducing an initial fill gas into theballoon in vivo; and a polymeric wall comprising one or more layers,wherein the polymeric wall is configured to have, under in vivoconditions, a permeability to CO₂ of more than 10 cc/m²/day, and whereinthe polymeric wall is configured such that, in vivo, the balloon gainsfrom 5 to 300% in volume and from 10% to 500% in pressure during auseful life of the intragastric balloon when filled with an initial fillgas, wherein the initial fill gas comprises an inert gas, and wherein aconcentration of one or more gases in the initial fill gas relative toan in vivo concentration of the one or more gases limits a rate and anamount of diffusion of the one or more gases from the in vivo gastricenvironment into the intragastric balloon through the polymeric wall.

In an embodiment of the third aspect, a concentration of CO₂ in theinitial fill gas relative to an in vivo CO₂ concentration limits a rateand an amount of diffusion of CO₂ from the in vivo gastric environmentinto the intragastric balloon through the polymeric wall.

In an embodiment of the third aspect, the initial fill gas furthercomprises one or more gases that are also present in the in vivo gastricenvironment.

In an embodiment of the third aspect, the initial fill gas consistsessentially of N₂.

In an embodiment of the third aspect, the initial fill gas consistsessentially of N₂ and CO₂.

In an embodiment of the third aspect, the initial fill gas consistsessentially of N₂, O₂, and CO₂.

In an embodiment of the third aspect, the polymeric wall comprises a CO₂barrier material consisting of nylon/polyvinylidenechloride/polyethylene.

In an embodiment of the third aspect, the polymeric wall comprises anylon/polyethylene material and no additional CO₂ barrier material.

In an embodiment of the third aspect, the useful life is at least 30days.

In a fourth aspect, a method is provided for inflating an intragastricballoon, comprising: providing an intragastric balloon comprising avalve system and a polymeric wall, wherein the polymeric wall comprisesone or more layers, and wherein the polymeric wall is configured tohave, under in vivo conditions, a permeability to CO₂ of more than 10cc/m²/day; introducing, in an in vivo intragastric environment, aninitial fill gas into the intragastric balloon through the valve systemto an initial volume and an initial pressure, wherein the initial fillgas comprises an inert gas, and wherein a concentration of one or moregases in the initial fill gas relative to an in vivo concentration ofthe one or more gases limits a rate and an amount of diffusion of theone or more gases from the in vivo gastric environment into theintragastric balloon through the polymeric wall; and exposing the filledballoon to the in vivo intragastric environment for a useful life of theintragastric balloon, whereby the initial fill gas diffuses through thepolymeric wall and into the in vivo intragastric environment, andwhereby gases in the in vivo intragastric environment diffuse into theballoon through the wall, whereby the intragastric balloon gains from 5to 300% in volume and from 10% to 500% in pressure over the useful life.

In an embodiment of the fourth aspect, the polymeric wall comprises aCO₂ barrier material consisting of nylon/polyvinylidenechloride/polyethylene.

In an embodiment of the fourth aspect, the polymeric wall comprises aCO₂ barrier material consisting of nylon/polyethylene and no additionalCO₂ barrier material.

In an embodiment of the fourth aspect, a concentration of CO₂ in theinitial fill gas relative to an in vivo CO₂ concentration limits a rateand an amount of diffusion of CO₂ from the in vivo gastric environmentinto the intragastric balloon through the polymeric wall.

In an embodiment of the fourth aspect, the initial fill gas furthercomprises one or more gases that are also present in the in vivo gastricenvironment.

In an embodiment of the fourth aspect, the inert gas is N₂.

In an embodiment of the fourth aspect, the initial fill gas consistsessentially of N₂ and CO₂.

In an embodiment of the fourth aspect, N₂ is excess in concentration toCO₂ in the initial fill gas.

In an embodiment of the fourth aspect, the initial fill gas consistsessentially of N₂ and O₂.

In an embodiment of the fourth aspect, N₂ is in excess in concentrationto O₂ in the initial fill gas.

In an embodiment of the fourth aspect, the initial fill gas consistsessentially of N₂, O₂, and CO₂.

In an embodiment of the fourth aspect, N₂ is excess in concentration toO₂ and CO₂ combined in the initial fill gas.

In an embodiment of the fourth aspect, the useful life is at least 30days.

In a fifth aspect, an intragastric balloon is provided, comprising: avalve system configured for introducing an initial fill gas into theballoon in vivo; and a polymeric wall comprising one or more layers,wherein the polymeric wall is configured to have, under in vivoconditions, a permeability to CO₂ of more than 10 cc/m²/day, and whereinthe polymeric wall is configured such that, in vivo, the balloon gainsfrom 5 to 300% in volume and from 10% to 500% in pressure during auseful life of the intragastric balloon when filled with an initial fillgas, wherein the initial fill gas comprises an inert gas, wherein a rateand an amount of diffusion of CO₂ from the in vivo gastric environmentinto the intragastric balloon through the polymeric wall is controlled,at least in part, by a concentration of one or more gases in the initialfill gas, and wherein the useful life is at least 30 days.

The intragastric balloon of Claim 1, wherein the intragastric balloon isconfigured such that a concentration of CO₂ in the initial fill gasrelative to an in vivo CO₂ concentration limits a rate and an amount ofdiffusion of CO₂ from the in vivo gastric environment into theintragastric balloon through the polymeric wall.

In an embodiment of the fifth aspect, the polymeric wall comprises a CO₂barrier material consisting of nylon/polyvinylidenechloride/polyethylene.

In an embodiment of the fifth aspect, the polymeric wall comprises anylon/polyethylene material and no additional CO₂ barrier material.

In an embodiment of the fifth aspect, the inert gas is N₂, and whereinthe initial fill gas consists essentially of N₂.

In an embodiment of the fifth aspect, the inert gas is N₂, and whereinthe initial fill gas consists essentially of N₂ and CO₂.

In an embodiment of the fifth aspect, the inert gas is N₂, wherein theinitial fill gas consists essentially of N₂ and CO₂, and wherein N₂ isexcess in concentration to CO₂ in the initial fill gas.

In an embodiment of the fifth aspect, the inert gas is N₂, and whereinthe initial fill gas consists essentially of N₂, O₂, and CO₂.

In an embodiment of the fifth aspect, the inert gas is N₂, wherein theinitial fill gas consists essentially of N₂, O₂, and CO₂, and wherein N₂is excess in concentration to CO₂ and O₂ combined in the initial fillgas.

In a sixth aspect, a method for inflating an intragastric balloon isprovided, comprising: providing an intragastric balloon comprising avalve system and a polymeric wall, wherein the polymeric wall comprisesone or more layers, and wherein the polymeric wall is configured tohave, under in vivo conditions, a permeability to CO₂ of more than 10cc/m²/day; introducing, in an in vivo intragastric environment, aninitial fill gas into the intragastric balloon through the valve systemto an initial volume and an initial pressure, wherein the initial fillgas comprises an inert gas, wherein a rate and an amount of diffusion ofCO₂ from the in vivo gastric environment into the intragastric balloonthrough the polymeric wall is controlled, at least in part, by aconcentration of one or more gases in the initial fill gas; and exposingthe filled balloon to the in vivo intragastric environment for a usefullife of the intragastric balloon, whereby the initial fill gas diffusesthrough the polymeric wall and into the in vivo intragastricenvironment, and whereby gases in the in vivo intragastric environmentdiffuse into the balloon through the wall, whereby the intragastricballoon gains from 5 to 300% in volume and from 10% to 500% in pressureover the useful life, wherein the useful life is at least 30 days.

In an embodiment of the sixth aspect, a concentration of CO₂ in theinitial fill gas relative to an in vivo CO₂ concentration limits a rateand an amount of diffusion of CO₂ from the in vivo gastric environmentinto the intragastric balloon through the polymeric wall.

In an embodiment of the sixth aspect, the polymeric wall comprises a CO₂barrier material consisting of nylon/polyvinylidenechloride/polyethylene.

In an embodiment of the sixth aspect, the polymeric wall comprises a CO₂barrier material consisting of nylon/polyethylene and no additional CO₂barrier material.

In an embodiment of the sixth aspect, the inert gas is N₂, and whereinthe initial fill gas consists essentially of N₂.

In an embodiment of the sixth aspect, the inert gas is N₂, and whereinthe initial fill gas consists essentially of N₂ and CO₂.

In an embodiment of the sixth aspect, the inert gas is N₂, wherein theinitial fill gas consists essentially of N₂ and CO₂, and wherein N₂ isexcess in concentration to CO₂ in the initial fill gas.

In an embodiment of the sixth aspect, the inert gas is N₂, and whereinthe initial fill gas consists essentially of N₂, O₂, and CO₂.

In an embodiment of the sixth aspect, the inert gas is N₂, wherein theinitial fill gas consists essentially of N₂, O₂, and CO₂, and wherein N₂is excess in concentration to CO₂ and O₂ combined in the initial fillgas.

In a seventh aspect, an intragastric balloon is provided configured tohave a useful life in an in vivo gastric environment of at least 30days, comprising: a polymeric wall configured to have, under conditionsof an in vivo gastric environment, a permeability to CO₂ of more than 10cc/m²/day, such that a rate and an amount of diffusion of CO₂ from thein vivo gastric environment into a lumen of the balloon through thepolymeric wall is controlled, at least in part, by a concentration of aninert gas in an initial fill gas, wherein the polymeric wall comprisesone or more expandable sections configured to stretch from 10% to 400%in response to an increased volume of a fluid inside thevolume-occupying subcomponent; and a valve system configured forintroducing the initial fill gas into the lumen of the balloon in the invivo gastric environment.

In an embodiment of the seventh aspect, the polymeric wall comprises athree layer CO₂ barrier material consisting of nylon/polyvinylidenechloride/polyethylene.

In an embodiment of the seventh aspect, the polymeric wall comprises atwo layer CO₂ barrier material consisting of nylon/polyethylene materialand no additional CO₂ barrier material.

In an embodiment of the seventh aspect, the initial fill gas consistsessentially of SF₆ and N₂.

In an embodiment of the seventh aspect, the initial fill gas consistsessentially of SF₆.

In an embodiment of the seventh aspect, an entirety of the polymericwall is expandable.

In an embodiment of the seventh aspect, the intragastric ballooncomprises one or more non-expandable sections.

In an embodiment of the seventh aspect, the one or more expandablesections comprises a band positioned around any section of theintragastric balloon.

In an embodiment of the seventh aspect, the band wraps around acircumference of the instragastric balloon.

In an embodiment of the seventh aspect, the band has one or more curvedor angled sections.

In an embodiment of the seventh aspect, the one or more expandablesections comprises multiple bands of expandable material.

In an embodiment of the seventh aspect, the intragastric ballooncomprises one or more non-expandable bands positioned around any sectionof the intragastric balloon.

In an embodiment of the seventh aspect, the intragastric ballooncomprises a plurality of expandable panels.

In an embodiment of the seventh aspect, the expandable panels are eachthe same size.

In an embodiment of the seventh aspect, the intragastric ballooncomprises a plurality of nonexpandable panels.

In an embodiment of the seventh aspect, the nonexpandable panelscomprise a mesh.

In an embodiment of the seventh aspect, there are an equal number ofexpandable panels and nonexpandable panels.

In an embodiment of the seventh aspect, the intragastric ballooncomprises one or more expandable protrusions configured to protrude froma surface of the intragastric balloon.

In an embodiment of the seventh aspect, the polymeric wall comprises aplurality of layers, wherein one or more sections of the layers areexpandable.

In an eighth aspect, a method for inflating an intragastric balloon ofthe seventh aspect, comprising: introducing, in an in vivo intragastricenvironment, an initial fill gas comprising an inert gas into a lumen ofan intragastric balloon according to Claim 1; and exposing the balloonto the in vivo intragastric environment for a useful life of at least 30days, wherein a rate and an amount of diffusion of CO₂ from the in vivogastric environment into the lumen of the balloon through the polymericwall is controlled, at least in part, by a concentration of an inert gasin the initial fill gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an exemplary intragastricvolume-occupying device in an inflated state, in accordance with apreferred embodiment.

FIG. 1B is a cross-sectional view of an exemplary intragastricvolume-occupying device of FIG. 1A, with the cross-section being takenalong line 1B-1B.

FIG. 2A is a perspective view of an exemplary intragastricvolume-occupying device in a delivery state, in accordance with apreferred embodiment.

FIG. 2B is a cross-sectional view of an exemplary intragastricvolume-occupying device of FIG. 2A, with the cross-section being takenalong line 2B-2B.

FIG. 3A is a perspective view of an exemplary intragastricvolume-occupying device in a delivery state, in accordance with apreferred embodiment.

FIG. 3B is a cross-sectional view of an exemplary intragastricvolume-occupying device of FIG. 3A, with the cross-section being takenalong line 3B-3B.

FIG. 4A is a perspective view of an exemplary intragastricvolume-occupying device in a delivery state, in accordance with apreferred embodiment.

FIG. 4B is a cross-sectional view of an exemplary intragastricvolume-occupying device of FIG. 4A, with the cross-section being takenalong line 4B-4B.

FIG. 5A is a perspective view of an exemplary intragastricvolume-occupying device in a delivery state, in accordance with apreferred embodiment.

FIG. 5B is a cross-sectional view of an exemplary intragastricvolume-occupying device of FIG. 5A, with the cross-section being takenalong line 5B-5B.

FIG. 6 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 7 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 8 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 9 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 10 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 11 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 12 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 13 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 14 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 15 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state, in accordance with a preferredembodiment.

FIG. 16 is a perspective view of an exemplary volume-occupyingsubcomponent in an expanded state deployed within a patient's stomach,in accordance with a preferred embodiment.

FIG. 17 is a perspective view of an exemplary volume-occupyingsubcomponent including a band of expandable material, in accordance witha preferred embodiment.

FIGS. 18A-18B illustrate another exemplary volume-occupying devicetransitioning from a first state, wherein panels of expandable materialare unexpanded to a second state, wherein panels of expandable materialare expanded.

FIG. 19 is a perspective view of an exemplary volume-occupyingsubcomponent including an internal scaffold, in accordance with apreferred embodiment.

FIG. 20 is a perspective view of an exemplary volume-occupyingsubcomponent including a patch of expandable material, in accordancewith a preferred embodiment.

FIG. 21 is a perspective view of an exemplary volume-occupyingsubcomponent including a plurality of smaller volume-occupying devicesdisposed therein, in accordance with a preferred embodiment.

FIG. 22 is a perspective view of an exemplary volume-occupyingsubcomponent including a plurality of expandable structures, inaccordance with a preferred embodiment.

FIG. 23 is a perspective view of an exemplary volume-occupyingsubcomponent including a layers of expandable material therein, inaccordance with a preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 23 is a perspective view of an exemplary volume-occupyingsubcomponent including a layers of expandable material therein, inaccordance with a preferred embodiment.

The following description and examples illustrate a preferred embodimentof the present invention in detail. Those of skill in the art willrecognize that there are numerous variations and modifications of thisinvention that are encompassed by its scope. Accordingly, thedescription of a preferred embodiment should not be deemed to limit thescope of the present invention.

The term “degradable” as used herein is a broad term, and is to be givenits ordinary and customary meaning to a person of ordinary skill in theart (and is not to be limited to a special or customized meaning), andrefers without limitation to a process by which structural integrity ofthe balloon is compromised (e.g., by chemical, mechanical, or othermeans (e.g., light, radiation, heat, etc.) such that deflation occurs.The degradation process can include erosion, dissolution, separation,digestion, disintegration, delamination, comminution, and other suchprocesses. Degradation after a predetermined time, or within apredetermined window of time, after ingestion is particularly preferred.

The term “CO₂ barrier material” as used herein is a broad term, and isto be given its ordinary and customary meaning to a person of ordinaryskill in the art (and is not to be limited to a special or customizedmeaning), and refers without limitation to a material having apermeability to CO₂ of 10 cc/m²/day or less under simulated in vivoconditions (100% humidity and body temperature of 37° C.). As usedherein, the term “in vivo conditions” as used herein refers to bothactual in vivo conditions, such as in vivo intragastric conditions, andsimulated in vivo conditions. The permeability of a material to CO₂ mayvary depending upon the conditions under which it is measured.

The term “swallowable” as used herein is a broad term, and is to begiven its ordinary and customary meaning to a person of ordinary skillin the art (and is not to be limited to a special or customizedmeaning), and refers without limitation to ingestion of a balloon by apatient such that the outer capsule and its constituents are deliveredto the stomach via normal peristalsis movement. While the systems ofpreferred embodiments are swallowable, they are also configured byingestion by methods other than swallowing. The swallowability of thesystem is derived, at least in part, by the outer container size for theself-inflating system and the catheter and outer container size for themanual inflation system. For the self-inflating system, the outercapsule is sufficient to contain the inner container and itsconstituents, an amount of activation agent injected prior toadministration, the balloon size, and the balloon material thickness.The system is preferably of a size less than the average normalesophagus diameter.

Described herein is an orally ingestible device. In preferredembodiments, the device is able to traverse the alimentary canal. Thedevice may be useful, for example, as an intragastric volume-occupyingdevice. The device overcomes one or more of the above-described problemsand shortcomings found in current intragastric volume-occupying devices.

FIGS. 1A-1B illustrate an exemplary device 10 in an inflated stateaccording to an embodiment. Certain preferred embodiments employ avolume-occupying subcomponent, an inflation subcomponent, a deflationsubcomponent, and a delivery subcomponent. In other preferredembodiments, a volume-occupying device is provided with an inflationsubcomponent and a delivery subcomponent. Devices according to theembodiments may further comprise a tracking subcomponent and/or a drugdelivery subcomponent. FIGS. 2A through 5B are illustrations of thedevices 10 according to the embodiments that are in a delivery state,e.g., the devices 10 are in a compact, non-inflated state. FIGS. 2A, 3A,4A, and 5A are perspective views of the devices 10 and FIGS. 2B, 3B, 4B,and 5B are cross-sectional views of the corresponding devices 10.Generally, in the delivery state, the device 10 is in the form of aningestible capsule or other similarly sized and shaped package.

In order to more clearly describe the subject matter of the preferredembodiments, different embodiments of the same subcomponent will bedescribed under a single relevantly-titled subheading. This organizationis not intended to limit the manner in which embodiments of differentsubcomponents may be combined in accordance with the various aspects andembodiments.

Swallowable Intragastric Balloon System

A swallowable, self-inflating or inflatable intragastric balloon systemaccording to selected preferred embodiments includes the followingcomponents: self-sealing valve system for addition of fluid to the lumenof the balloon or to the inner container (“valve system”), a balloon ina deflated and compacted state (“balloon”) and an outer capsule,container, or coating (“outer container”) that contains the balloon. Forself-inflating balloons, an inner capsule or other container (“innercontainer”) that contains one or more CO₂ generating components ispresent inside the lumen of the balloon. For inflatable balloons, aninflation fluid source, a catheter, and tubing (“inflation assembly”)are provided for inflating the balloon after ingestion or placement inthe stomach. In the self-inflating balloon configuration, the valve ispreferably attached to the inner surface of the balloon by an adhesiveor other means (e.g., welding), and provided with an inoculation spacerto prevent puncture of the wall of the balloon and inner container by aneedle or other means for injecting an liquid activation agent into thelumen of the balloon via the self-sealing valve. A valve providingreleasable attachment of the tubing to the balloon is provided in theinflatable balloon configuration. Preferably, the self-sealing valvesystem attached to the balloon (e.g., on its inside surface) in theinflatable configuration is “universal” or compatible with a swallowablecatheter or a physician-assisted catheter. The valve system serves toallow for balloon inflation using a miniature catheter that includes aneedle assembly and also provides a mechanism for detachment of thecatheter after inflation has been completed.

The outer container preferably incorporates the balloon in a compactedstate (e.g., folded and rolled), preferably with sufficient space toallow for activation liquid to be injected into the balloon in theself-inflating balloon configuration, wherein the liquid activationagent initiates separation, erosion, degradation, and/or dissolution ofthe inner container and generation of CO₂ upon contact with theinflation agent contained within the inner container, which subsequentlycauses outer container separation, erosion, degradation, and/ordissolution due to CO₂ gas pressure. In the inflatable balloonconfiguration, the outer container need only incorporate the balloon ina compacted state.

Selected components of a swallowable intragastric balloon system of apreferred embodiment can include a silicone head with radioopacity ring,trimmed 30 D silicone septum, Nylon 6 inoculation spacer, compactedballoon, inner container (if self-inflating), and outer container asconstituents of the system in unassembled form. A fully assembled outercontainer can include a vent hole aligned with a septum for puncture toinject liquid activation agent (if self-inflating) or a port forconnection of tubing (if inflatable). As discussed further below, thecomponents of particularly preferred systems possess the attributesdescribed herein; however, in certain embodiments systems can beemployed which utilize components having other attributes and/or values.

Devices according to the preferred embodiments are intended foringestion by a patient and deployment without the need to resort toinvasive methods. It is therefore desirable that the device of thepreferred embodiments be operable to conform to a compact delivery statewhich can be swallowed by a patient with minimal discomfort. Once in thestomach, it is desirable for the device to assume a substantially largerdeployed state. In order to achieve the transition from a delivery stateto a deployed state the device is subjected to inflation.

Inner Container

In order to initiate inflation in the self-inflating configuration, theinflation subcomponent may require outside inputs such as an activationagent. The activation agent is preferably injected using a syringehaving a needle with a gauge diameter of from 25 to 32. The needlelength is preferably from about 0.25 inches (0.6 cm) to 1 inches (2.54cm) in length so as to create a flow rate that allows for delivery ofthe full volume of inflation agent within 30 seconds, but in amanner/stream/flow that does not physically damage the inner container,thereby causing premature CO₂ generation and inflation. The activationagent is preferably pure water, or a solution containing up to 50%concentration of anhydrous citric acid at 20° C., or the equivalentthereof at varying solution temperatures based on solubility ofanhydrous citric acid. Preferably, the system is configured to have anoccupyable void space in the central lumen of the balloon when incompacted form in the outer container of from about 0.3 ml to about 4.5ml, such that a corresponding volume of activation agent can be injectedinto the void space.

In one embodiment, prior to folding, the free-floating inner containerwith inflation agent for CO₂ generation is preferably vertically alignedwith the self-sealing valve system such that the septum/inoculationspacer is placed directly above the tip of the capsule. The ballooncontains an inner container. A self-sealing valve system is adhesivelyadhered to the interior of the wall of the balloon, and the invertedconfiguration of the balloon is provided by inversion through a holesealed with a patch. The top approximate ¼ of the balloon wall is foldedover the inner capsule, and the pleats where the capsule is are creasedsimilar to the pleats formed in the second step of making a paperairplane, then folded over to the left or to the right. The bottomapproximate ¾ of the sphere is then accordioned using no more than 2creases and folded over the capsule. The left half is then folded overthe right half of the capsule or vice versa so that the wings touch.Then the material is rolled over until it creates a tight roll. Thedevice is then placed inside the outer container.

In a self-inflating configuration, the balloon is folded so as to form apocket around the inner capsule, to insure that the liquid injectedthrough the self-sealing valve system is contained in an area less than10% of the entire balloon surface area. It is not necessary to provide apocket in the inflatable configuration, as no inner capsule is provided.The balloon is folded such that the number of total folds is minimizedso as to minimize possible damage to the outer material or compromise ofbarrier properties. The number of total folds is preferably less than 10folds. The balloon material is rolled when at all possible such that thenumber of creases required to fit the balloon in an outer container isminimized. This is done in effort to also to prevent lumen materialdamage. The self-sealing valve is also preferably constructed off-centerof the balloon so as to minimize the number of folds that layer on topof each other.

In the self-inflating configuration, the material forming the wall ofthe balloon is processed and folded to maximize reaction efficiency bylocalizing the initiation agent injected into the balloon so that it ismaintained proximal to the reactants within the inner container. Theballoon is folded such that once the reaction initiates and the outercontainer separates, the balloon unfolds in a manner that creates thelargest possible surface area, which prohibits the balloon from readilypassing through the pyloric sphincter. The ratio of reactants in theinflation agent and activation agent are selected such that the pH ofany remnant liquid inside the lumen of the balloon is acidic, with a pHof less than 6, such that any balloon leakage or breach that allowsstomach acid to enter does not cause additional CO₂ generation andresulting unintentional re-inflation.

In a self-inflating configuration, an inflation agent is compressed,formed or otherwise held in a shape which provides good surface areaavailability for the reactants for CO₂ generation, while minimizing thespace and/or volume sufficient to hold the inner container. Preferably,the inner container has a length (longest dimension) of from about 0.748inches (1.9 cm) to 1.06 inches (2.7 cm) and a diameter or width of fromabout 0.239 inches (0.6 cm) to about 0.376 inches (1 cm). The volume ofthe inner container is preferably from about 0.41 ml to about 1.37 ml.The inner container is preferably in the form of a standard push-fitgelatin capsule but a gelatin tape may be used in lieu of a push-fitcapsule. The container is preferably relied upon for containing theinflation agent; however, additional sealing or other encapsulation canbe employed to control timing of inflation. Gelatin is particularlypreferred for use as the inner container; however other materials canalso be suitable for use, e.g., cellulose. In order to minimize theinternal volume of the system, it is generally preferred to include onlya single inner container; however, in certain embodiments two or moreinternal containers can advantageously be employed. Timing ofself-inflation is selected based on a normal esophageal transit time anda normal time of gastric emptying of large food particles, such that theballoon does not inflate to a size that can block the esophagealpassageway or prematurely pass through the pyloric sphincter. Timing isalso controlled by compacting the balloon such that the activation agentis substantially localized in the balloon next to the inner capsule,creating an efficient CO₂ self-inflation method. Balloon inflation isinitiated by the liquid activation agent causing degradation of theinner container, such that the inflation agent in the inner containercontacts the liquid activation agent, thereby initiating the gasgeneration reaction.

Inflation Assembly

In certain preferred embodiments, the volume-occupying subcomponent isfilled with a fluid using tubing which is subsequently detached andpulled away from the volume-occupying subcomponent. One end of thevolume-occupying subcomponent has a port connected to tubing ofsufficient length that when unwound can span the entire length of theesophagus, from mouth to stomach. This tubing is connected to thevolume-occupying subcomponent with a self-sealable valve or septum thatcan tear away from the volume-occupying subcomponent and self-seal oncethe volume-occupying subcomponent is inflated. A physician or otherhealth care professional secures one end of the tubing as the patientswallows the device. Once the device is residing within the stomach, thephysician uses the tube to transmit a fluid, such as air, other gas(es),saline solution, pure water, or the like, into the volume-occupyingsubcomponent and thereby inflate it. After the volume-occupyingsubcomponent is fully inflated, the tubing is released and can be pulledout from inside the patient.

The tube may be released in a number of manners. For example, the tubingmay be detached by applying a gentle force, or tug, on the tubing.Alternatively, the tubing may be detached by actuating a remote release,such as a magnetic or electronic release. Additionally, the tubing maybe released from the volume-occupying subcomponent by an automaticejection mechanism. Such an ejection mechanism may be actuated by theinternal pressure of the inflated volume-occupying subcomponent. Forexample, the ejection mechanism may be sensitive to a specific pressurebeyond which it will open so as to release any excess pressure andsimultaneously release the tube. This embodiment provides a desirablefeature through combining release of the tubing with a safety valve thatserves to avert accidental over inflation of the volume-occupyingsubcomponent in the patient's stomach.

This automatic release embodiment also provides the benefit that thedevice inflation step may be more closely monitored and controlled.Current technology allows for a self-inflating intragastricvolume-occupying subcomponent which generally begins to inflate in afour minute timeframe after injection with an activation agent such ascitric acid. In this approach, the volume-occupying subcomponent may, insome instances, begin to inflate prior to residing within the stomach(e.g., in the esophagus), or, in patients with gastric dumping syndromeor rapid gastric emptying, the volume-occupying subcomponent may end upin the small intestine prior to the time that inflation occurs.Accordingly, in certain embodiments it can be desirable to inflate thevolume-occupying subcomponent on command, once it is ascertained thatthe volume-occupying subcomponent is residing in the correct location.

In certain embodiments, it may also be advantageous for thevolume-occupying subcomponent to inflate gradually or in several stepsover time, or for the volume-occupying subcomponent to maintain a volumeand/or internal pressure within a preselected range. For example, if gasescapes the volume-occupying subcomponent prior to the desired deflationtime, it can be beneficial for the device to re-inflate in order topreserve it in its expanded state.

Outer Container

The balloon is preferably provided in a deflated and folded state in acapsule or other retaining, containing or coating structure (“outercontainer”). The outer container is preferably in the form of a standardpush-fit gelatin capsule, with the push-fit relied upon for containingthe deflated/folded balloon; however, a gelatin wrap can advantageouslybe employed in certain embodiments. Gelatin is particularly preferredfor use as the outer container; however other materials can also besuitable for use, e.g., cellulose, collagen, and the like. Preferably,the outer container has a length (longest dimension) of from about 0.95inches (2.4 cm) to 2.5 inches (6.3 cm) and a diameter or width of fromabout 0.35 inches (0.9 cm) to about 0.9 inches (2.4 cm). The volume ofthe inner container is preferably from about 1.2 ml to about 8.25 ml. Inthe self-inflating configuration, the outer container is preferablyconfigured with one or more holes, slits, passageways or other egresses,preferably on each end, which act as vents such that any gas created dueto inflation agent exposure to condensation or other ambient moisturepresent during processing does not cause premature separation ordegradation of the inner container prior to 30 seconds after inoculationof the liquid activation agent, which may have an undesirable effect onreaction efficiency. Such egresses can also expedite dissolution of theouter container to prepare the balloon for inflation in the inflatableconfiguration. The process of the outer capsule degrading (e.g.,separates, dissolves, or otherwise opens) is expedited by pressure buildup caused by inflation (self-inflation or inflation via catheter) of theballoon. The outer capsule can be dipped in water for a brief time tosoften the materials but not release the balloon prior to swallowing tominimize the time lapse between swallowing and balloon inflation. In theinflatable configuration, the outer container is provided with a hole tohouse the inflation tube needle assembly, wherein the diameter of thecatheter needle housing is mechanically compatible with the diameter ofthe outer container hole such that the needle can be inserted into theself-sealing valve while maintaining therein the housed balloon tofacilitate pushing or swallowing of the balloon assembly. In a preferredembodiment, the outer container is a capsule. The distal half of thecapsule may be flared to prevent abrasion of the balloon materials bythe leading edge of the capsule as the compacted balloon is insertedinto the capsule. The capsule can also comprise two parts held togetherwith a gel band and encompassing the folded balloon that allows forquicker separation of the capsule so that inflation can take place moreexpeditiously. The outer capsule degrades (e.g., separates, dissolves,or otherwise opens) due to contact with ingested fluid ingestion (e.g.,water intake) and preferably degrades within 5 minutes or less, morepreferably within 2 minutes or less, so as not to cause discomfort tothe patient while the balloon/catheter tube is in place.

In a preferred embodiment, the device is fitted into a standard sizedgelatin capsule. The capsule may be formed of a material that has aknown rate of degradation such that the device will not be released fromthe capsule or otherwise deployed prior to entry into the stomach. Forexample, the capsule materials may include one or more polysaccharideand/or one or more polyhydric alcohols.

Alternatively, the device, in its delivery state, may be coated in asubstance that confines the device in its delivery state while alsofacilitating swallowing. The coating may be applied by a dipping,sputtering, vapor deposition, or spraying process which may be conductedat an ambient or positive pressure.

In certain preferred embodiments, the encapsulated or coated device islubricated or otherwise treated so as to facilitate swallowing. Forexample, the encapsulated or coated device may be wetted, heated, orcooled, prior to swallowing by the patient. Alternatively, theencapsulated or coated device may be dipped in a viscous substance thatwill serve to lubricate the device's passage through the esophagus.Examples of possible coatings can be any substances with lubriciousand/or hydrophilic properties and include glycerine,polyvinylpyrrolidone (PVP), petroleum jelly, aloe vera, silicon-basedmaterials (e.g. Dow 360) and tetrafluoroethylene (TFE). The coating mayalso be applied by a sputtering, vapor deposition or spraying process.

In additional embodiments the coating or capsule is impregnated ortreated with one or more local anesthetics or analgesics to easeswallowing. Such anesthetics may include anesthetics in the amino amidegroup, such as articaine, lidocaine and trimecaine, and anesthetics inthe amino ester group, such as benzocaine, procaine and tetracaine. Suchanalgesics may include chloraseptic.

In certain embodiments, the capsule may be weighted at a certain end inorder for it to be oriented appropriately when it is administered, as ittravels down the esophagus, and/or when it is in the stomach. Theweighting components may include polymer materials or inflationreactants.

The swallowable, self-inflating intragastric balloon is provided withmechanisms to reliably control timing of self-inflation such thatpremature inflation while in the esophagus during swallowing is avoidedand sufficient inflation once in the stomach so as to prevent passagethrough the pyloric sphincter is ensured. Normal esophageal transit timefor large food particles has been documented as 4-8 seconds, and gastricemptying of large food particles through the pylorus does not occur forat least 15-20 minutes. The outer container is preferably configured toseparate, dissolve, degrade, erode, and/or otherwise allow thedeflated/folded balloon to begin unfolding not less than 60 seconds butnot more than 15 minutes after inoculation with liquid activation agent.The inner container is preferably configured chemically, mechanically ora combination thereof to retard the initial CO₂ generating chemicalreaction such that sufficient CO₂ to begin inflating the balloon is notavailable earlier than 30 seconds after inoculation with the liquidactivation agent, but to permit generation of sufficient CO₂ such thatat least 10% of the occupyable volume of the balloon is filled within 30minutes, at least 60% of the occupyable volume of the balloon is filledwithin 12 hours, and at least 90% of the occupyable volume of theballoon is filled within 24 hours. This timing allows for injection ofthe activation agent into the outer container by the medicalprofessional, passing the device to the patient, and swallowing bynormal peristaltic means by the patient. This timing also prohibitspotential passing of an uninflated balloon into the duodenum by theballoon being inflated to a sufficient size such that gastric emptyingof the balloon cannot be easy, as objects more than 7 mm in diameter donot readily pass.

Delivery Components

It certain embodiments, it may advantageous for an administrator of thedevice to use a delivery tool for delivering the device to the mouth orfacilitating its passage through the esophagus in the optimalorientation. A delivery tool may enable the device administrator toinject the device with one or more inflation agents or inflation gasesas part of administering the device to the patient. In a preferredembodiment, such injection may be accomplished in the same mechanicalaction(s) of the administrator that are employed to release the devicefrom the delivery tool into the mouth or esophagus. For example, thedelivery tool may include a plunger, a reservoir containing a fluid, andan injection needle. The administrator pushes the plunger which, eitherin sequence or approximately simultaneously, forces the injection needleinto the device and thereby injects the liquid contained in reservoirinto the device. Subsequent application of force to the plunger pushesthe device out of the delivery tool and into the desired location withinthe patient. Furthermore, the delivery tool may also include asubcomponent that administers an anesthetic or lubricant into thepatient's mouth or esophagus to ease the swallowability of the device.

Balloon

The volume-occupying subcomponent (“balloon”) of the preferredembodiments is generally formed of a flexible material forming a wallwhich defines an exterior surface and an interior cavity. Various of theabove-described subcomponents may be either incorporated into the wallor interior cavity of the volume-occupying subcomponent. FIGS. 6-23depict various volume-occupying subcomponents 100. As shown,volume-occupying subcomponent 100 will vary in size and shape accordingto the patient's internal dimensions and the desired outcome. Thevolume-occupying subcomponent 100 may be engineered to besemi-compliant, allowing the volume-occupying subcomponent 100 tostretch or expand with increases in pressure and/or temperature. Forexample, the volume-occupying subcomponent 100 may be filled with afluid that expands over time, such as SF₆, after the volume-occupyingdevice is deployed into the patient's stomach and inflated with saidfluid. Alternatively, in some embodiments, a compliant wall offeringlittle resistance to increases in volume may be desirable. In someembodiments, the entirety of the volume-occupying subcomponent isexpandable, meaning that the volume-occupying subcomponent 100 canstretch in response to an increased volume of the fluid (liquid or gas)inside the volume-occupying subcomponent. In other embodiments, thevolume-occupying subcomponent includes one or more expandable sections.

FIGS. 17-23 illustrate various volume-occupying subcomponents 100 havingone or more expandable sections. As shown in FIG. 17, the body 110 ofthe volume-occupying subcomponent 100 includes or incorporates a band120 of stretchable or expandable material. The band 120 of material maybe co-extruded with the polymer film of the volume-occupyingsubcomponent 100 or welded onto the formed upper and lower portions 130,140, respectively, of the volume-occupying subcomponent 100. Forexample, in the illustrated embodiment, the band 120 is welded at theseam 450 of the volume-occupying subcomponent 100. In alternativeembodiments, the volume-occupying subcomponent 100 may include multiplebands 120 of stretchable material. Other embodiments may include one ormore non-expanding or minimally expanding bands. As depicted in FIG. 17,the band 120 is wrapped around the center of the sphericalvolume-occupying subcomponent 100. However, bands 120 may be positionedaround any section of the volume-occupying subcomponent 100. In someembodiments, one or more stretchable bands 120 may wrap around only partof the volume occupying subcomponent 100. Although the band 120 is shownas a straight line wrapping around the spherical volume-occupyingsubcomponent 100, it is contemplated that a band 120 may have curved orangled sections.

FIGS. 18A-18B show another volume-occupying subcomponent 100 having aplurality of stretchable panels 160 that can stretch to an expandedstate. FIG. 18A, shows the panels 160 of the volume-occupying device 100in a relaxed or unstretched state. FIG. 18B, shows the panels 160 of thevolume-occupying device 100 in an expanded or stretched state. In someembodiments, each stretchable panel 160 is the same size. In someembodiments, there are several stretchable panels 160 of varying sizes.In some embodiments, there are an equal number of stretchable panels 160and non-stretchable panels. In some embodiments, there are morestretchable panels 160 than non-stretchable panels. In some embodiments,there are fewer stretchable panels 160 than non-stretchable panels. Inpreferred embodiments, the panels 160 stretch over a period of time as aresult of fluid expansion within the volume-occupying subcomponent 100.

FIG. 19 shows a volume-occupying subcomponent 100 having an internalscaffold or mesh including a plurality of stretchable sections 170. Insome embodiments, each section 170 in the scaffold or is stretchable. Insome embodiments, the scaffold or mesh can include one or morenon-expanding or minimally expanding scaffold or mesh sections. In someembodiments, the scaffold or mesh webbing may be expandable. In someembodiments, the scaffold or mesh webbing is non-expandable or minimallyexpandable. In some embodiments, each section 170 is the same size. Insome embodiments, one or more sections 170 may be of varying sizes.

FIG. 20 shows a volume-occupying subcomponent 100 having an expandablepatch segment 180. Some embodiments may have more than one expandablepatch segments 180. Some embodiments may include one or morenon-expandable or minimally expandable patch segments.

FIG. 21 shows a volume-occupying subcomponent 100 having a plurality ofexpandable spheres, bubbles or bladders 190. Some embodiments includesome non-expandable spheres. In some embodiments, each expandable sphere190 is the same size. In some embodiments, the expandable spheres 190can be of varying sizes. Different expandable shapes are also possible.In some embodiments, a volume-occupying subcomponent 100 can includemultiple different expandable shapes therein.

FIG. 22 shows a volume-occupying subcomponent 100 having a plurality ofexpandable protrusions 200 extending outwardly from the surface 210 ofthe volume-occupying subcomponent 100. Each protrusion 200 can be of thesame size or the protrusions 200 can be of several different sizes. Insome embodiments, the protrusions 200 can be of several differentshapes, or each protrusion 200 may be of the same shape.Volume-occupying subcomponent designs are not limited to theseembodiments and may include any number or configuration of expandablebands, panels, mesh sections, patch segments, shperes and protrusions.In some embodiments of volume-occupying subcomponents 100 havingexpandable sections, the volume-occupying subcomponents 100 may furtherinclude one or more rigid sections, non-expanding or minimally expandingsections.

FIG. 23 shows a volume-occupying subcomponents 100 having several layersor bladders In this embodiment, the volume-occupying subcomponent 100having a first layer 230 therein and a second layer 240 within the firstlayer 230. One or more sections of the layers 230 and 240 can beexpandable. In a volume-occupying subcomponent 100 having severallayers, the layers may be constructed and configured so as to haveminimal or no impact on the expandability of the expandable sections. Inother embodiments, the layers 230, 240 are constructed and configured soas to expand at different rates.

In some embodiments, the volume-occupying subcomponents 100 can beconstructed of from less than 10% expandable material to 100% expandablematerial. In some embodiments, the volume-occupying subcomponent caninclude 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% expandablematerials.

Expandable sections may be constructed of one or more stretchablematerials allowing for expansion of the fluid inside thevolume-occupying subcomponent. The external surfaces of the volumeoccupying subcomponents are constructed of materials compatible with thegastric environment. Examples of some materials that may be included inthe expandable sections are listed in Tables 1a-b and 2. In someembodiments, the stretchable material may stretch to from less than 10%to greater than 400% more than the unstretched size of the material. Insome embodiments, the stretchable material may stretch from between 10%and 50%, between 50% and 100%, between 100% and 150%, between 150% and200%, between 200% and 250%, between 250% and 300%, between 300% and350%, and between 350% and 400% more than the original size of thematerial. In some embodiments, the stretchable material may stretch to10%, 50%, 100%, 150%, 200%, 250%, 300%, 350%, and 400% more than theunstretched size of the material. In some embodiments, multipleexpandable volume-occupying subcomponents may be used simultaneously.

Spherical or eliptical volume-occupying subcomponents 100 are preferredin certain embodiments. Alternatively, the volume-occupying subcomponent100 may be constructed to be donut-shaped, see FIGS. 9 and 16, with ahole 220 or through-channel in the middle of it, and may be weighted andshaped in such a way that it orients in the stomach to cover all or partof the pyloric sphincter, similar to a check valve. The hole 220 in themiddle of the volume-occupying subcomponent 100 can then serve as theprimary passage for the contents of the stomach to enter the smallintestine, limiting the passage of food out of the stomach and inducingsatiety by reducing gastric emptying. Volume-occupying subcomponent 100may be manufactured with different-sized donut-holes 220 according tothe degree that gastric emptying is desired to be reduced. Delivery,inflation and deflation of the volume-occupying subcomponent 100 may beaccomplished by any of the methods described above.

It is advantageous for the volume-occupying subcomponent wall to be bothhigh in strength and thin, so as to minimize the compacted volume of thedevice as it travels the esophagus of the patient. In certainembodiments, the volume-occupying subcomponent wall materials aremanufactured with a biaxial orientation that imparts a high modulusvalue to the volume-occupying subcomponent.

In one embodiment, the volume-occupying subcomponent is constructed of apolymeric substance such as polyurethane, polyethylene terephthalate,polyethylene naphthalate, polyvinyl chloride (PVC), Nylon 6, Nylon 12,or polyether block amide (PEBA). The volume-occupying subcomponent maybe coated with one or more layers of substances that modify (increase,reduce, or change over time) gas-barrier characteristics, such as athermoplastic substance.

Preferably, the gas-barrier materials have a low permeability to carbondioxide or other fluids that may be used to inflate the volume-occupyingsubcomponent. The barrier layers should have good adherence to the basematerial. Preferred barrier coating materials include biocompatiblepoly(hydroxyamino ethers), polyethylene naphthalate, polyvinylidenechloride (PVDC), saran, ethylene vinyl alcohol copolymers, polyvinylacetate, silicon oxide (SiOx), acrylonitrile copolymers or copolymers ofterephthalic acid and isophthalic acid with ethylene glycol and at leastone diol. Alternative gas-barrier materials may includepolyamine-polyepoxides. These materials are commonly acquired as asolvent or aqueous based thermosetting composition and are generallyspray-coated onto a preform and then heat-cured to form the finishedbarrier coating. Alternative gas-barrier materials which may be appliedas coatings to the volume-occupying subcomponent include metals such assilver or aluminum. Other materials that may be used to improve the gasimpermeability of the volume-occupying subcomponent include, but are notlimited to, gold or any noble metal, PET coated with saran, conformalcoatings and the like, as listed, for example, in Tables 1a-b.

In certain preferred embodiments, the volume-occupying subcomponent isinjection, blow or rotational molded. Either immediately following suchmolding, or after a period of curing, the gas-barrier coating may beapplied if not already applied within the composite wall.

In another embodiment, the intragastric volume-occupying subcomponent isformed using a Mylar polyester film coating silver, aluminum orkelvalite as a metalized surface, to improve the gas impermeability ofthe volume-occupying subcomponent.

In the event that the volume-occupying subcomponent's wall is composedof multiple layers of materials, it may be necessary to use certainsubstances or methods to connect, attach or hold together such multiplelayers. Such substances can include a solvent or an ether-basedadhesive. Such multiple layers may also be heat-bonded together. Oncesuch layers are attached together to form (for example) a sheet ofmaterial to be made into a volume-occupying subcomponent, it may also benecessary to apply additional treatment steps to such material to allowit to seal together (for example, by application of a certain degree ofheat and pressure) in order to be made into a volume-occupyingsubcomponent. Accordingly, it may be advantageous to include as anadditional layer in the volume-occupying subcomponent certain materialsthat seal. For example, a volume-occupying subcomponent comprised of acombination of PET and SiOx layers, which impart favorable mechanicaland gas impermeability characteristics to the volume-occupyingsubcomponent, may be sealed by including a layer of sealablepolyethylene in such volume-occupying subcomponent.

According to another embodiment of the preferred embodiments, thefunctionality of the volume-occupying subcomponent and the deflationcomponent is combined either in part or in whole. For example, thevolume-occupying subcomponent may be formed of a substance that isdegraded within the stomach over a desired period of time. Once thedegradation process has formed a breach in the wall of thevolume-occupying subcomponent, the volume-occupying subcomponentdeflates, continues to degrade and passes through the remainder of thedigestive tract.

Preferably, an automated process is employed that takes a fullyconstructed volume-occupying subcomponent, evacuates all of the airwithin the interior cavity and folds or compresses the volume-occupyingsubcomponent into the desired delivery state. For example, theevacuation of air from the volume-occupying subcomponent may be actuatedby vacuum or mechanical pressure (e.g. rolling the volume-occupyingsubcomponent). In certain embodiments, it is desirable to minimize thenumber of creases produced in the volume-occupying subcomponent when inthe delivery state.

Deflation and/or inflation of the volume-occupying subcomponent may beachieved through one or more injection sites within the wall of thevolume-occupying subcomponent. For example, two self-sealing injectionsites can be incorporated at opposite sides of the volume-occupyingsubcomponent. The volume-occupying subcomponent may be positioned withina fixture that employs two small-gauge needles to evacuate the air fromthe volume-occupying subcomponent.

In one embodiment, the self-sealing injection sites may further be usedto insert chemical elements of the inflation subcomponent into theinterior of the volume-occupying subcomponent. After injection of thechemical elements into the volume-occupying subcomponent, the sameneedles may be used to perform evacuation of the volume-occupyingsubcomponent.

It may be desirable that the volume-occupying subcomponent is packedinto the delivery state under, for example, a negative vacuum pressureor under a positive external pressure.

The volume-occupying subcomponent wall materials may also be engineeredto, once they are initially punctured or torn, tear relatively easilyfrom the point of such puncture or tear. Such properties can, forexample, be advantageous if deflation of the volume-occupyingsubcomponent were initiated by a tearing or puncturing of thevolume-occupying subcomponent wall, since such initial tear or puncturemay then increase in scope, hastening and/or maximizing the deflationprocess.

The volume-occupying subcomponent may also be coated by a lubricioussubstance that facilitates its passage out of the body following itsdeflation. Examples of possible coatings can be any substances withlubricious and/or hydrophilic properties and include glycerine,polyvinylpyrrolidone (PVP), petroleum jelly, aloe vera, silicon-basedmaterials (e.g. Dow 360) and tetrafluoroethylene (TFE). The coating maybe applied by a dipping, sputtering, vapor deposition or sprayingprocess which may be conducted at an ambient or positive pressure.

The balloon composite wall materials can be of similar construction andcomposition as those described in U.S. Patent Publication No.2010-0100116-A1, the contents of which is hereby incorporated byreference in its entirety. The materials are able to contain a fluid,such as a liquid or a gas in compressed or non-compressed gas form, suchas, e.g., N₂, Ar, O₂, CO₂, SF₆ or mixture(s) thereof, or atmospheric air(composed of a mixture of N₂, O₂, Ar, CO₂, Ne, CH₄, He, Kr, H₂, and Xe)that simulate gastric space concentrations. In certain embodiments, theballoon is able to hold the fluid and maintain an acceptable volume forup to 6 months, preferably for at least 1 to 3 months after inflation.Particularly preferred fill gases include non-polar, large moleculegases that can be compressed for delivery.

Prior to placement in the outer container, the balloon is deflated andfolded. In the inverted configuration in a deflated state, the balloonis flat, with the inverted seam extending around the perimeter of theballoon. The self-sealing valve system is affixed to the inner wall ofthe lumen close to the center of the deflated balloon, with the innercontainer positioned adjacent to the self-sealing valve system. Thewalls of the balloon are then folded. As part of the balloon design, theself-sealing valve system is manufactured in a manner such that it isplaced “off center” to minimize the number of folds upon themselves(e.g., doubling or tripling up) required to fit the balloon in the outercontainer. For example, the self-sealing valve system can advantageouslybe placed ½ r±¼ r from the center of the balloon, wherein r is theradius of the balloon along a line extending from the center of theballoon through the septum.

Tracking and Visualization Subcomponent

It may also be beneficial to implement tracking and visualizationfunctionality into devices according to the embodiments. Due to thenon-invasive nature of the present device, physicians may desire todetermine, or confirm, the location and orientation of the device priorto inflation or during the course of treatment.

Alternatively, the marker may be applied to the volume-occupyingsubcomponent when the volume-occupying subcomponent is in a creased orfolded state such that when the volume-occupying subcomponent is in itsdeflated state the marker appears concentrated when viewed onvisualization equipment, and when the volume-occupying subcomponent isinflated the marker appears less concentrated when viewed onvisualization equipment. Alternatively, the marker may be applied orincorporated into the volume-occupying subcomponent so as to facilitateidentification and location of the various subcomponents of the device,such as a valve, head, or weight. The marker may be printed or paintedonto a surface of the volume-occupying subcomponent or between layers ofthe material forming the volume-occupying subcomponent. Alternatively, ametal coating as described below may be used as a marker to identifyand/or locate the volume-occupying subcomponent. Metal coatings forvisualizing the volume-occupying subcomponent may include silver, gold,tantalum or any noble metal. Alternatively, the marker may be applied toan elastomeric sleeve that covers all or part of the volume-occupyingsubcomponent.

In another embodiment, the volume-occupying subcomponent incorporates asubcomponent that changes mechanically upon inflation of thevolume-occupying subcomponent, which mechanical change can be visualizedusing x-ray or other visualization equipment. For example, a mechanicalportion of the volume-occupying subcomponent containing a visualizationmarker may elongate upon an increase in pressure in the volume-occupyingsubcomponent.

Alternatively, a marker may be formed using a metalized mesh locatedbetween layers of the material from which the volume-occupyingsubcomponent is constructed. The pattern or patterns formed by theimbedded marker will appear when the volume-occupying subcomponent is inan inflated, deployed state.

It is envisioned that marker materials may be incorporated into thevolume-occupying subcomponent to facilitate various visualizationtechniques such as, for example, MRI, CT and ultrasound.

The volume-occupying subcomponent may also contain a dye or marker thatis released upon deflation to indicate that the volume-occupyingsubcomponent cavity has been breached. Such dye or marker may, forexample, be apparent in the patient's urine as an indication that thevolume-occupying subcomponent has begun to deflate.

In yet further embodiments, microchips and other components employingelectronic modalities may be used to locate and identify a device.Microchips analogous to those utilized for the identification of petsmay be used to communicate device specific information and itsapproximate location. For example, a Wheatstone or other bridge circuitmay be incorporated into the device and, together with RF “ping andlisten” technology may be used as part of a system to determine thedevice's approximate location and measure and communicate devicespecific information. Such device specific information can includeinternal volume-occupying subcomponent pressure, which can indicate thedegree of inflation of the volume-occupying subcomponent.

In yet further embodiments, mechanical, chemical, visual and othersensors may be included as part of the device to measure, record and/ortransmit information relating to the device and/or the patient'sinternal environment. For example, the device may contain a camera orany of the other imaging and transmission components of a Pillcamdevice. As an additional example, the device may contain sensors thatmeasure, record and/or transmit information relating to stomach pH,stomach pressure, hormone levels, organ health, and organ safety.

Valve System

In preferred embodiments, a self-sealing valve system which contains aself-sealing septum housed within a metallic concentric cylinder isprovided. In the inflatable configuration, the self-sealing valve systemis preferably adhered to the underside of the balloon material such thatonly a portion of the valve protrudes slightly outside of the balloonsurface to ensure a smooth surface. The valve system for the inflatableconfiguration can utilize the same self-sealing septum designed for theself-inflating configuration. The septum preferably consists of amaterial possessing a durometer of 20 Shore A to 60 Shore D. The septumis inserted or otherwise fabricated into the smaller cylinder of theconcentric metallic retaining structure that is preferably cylindricalin shape. The smaller cylinder within the larger cylinder controlsalignment of the catheter needle sleeve/needle assembly with the septum,provides a hard barrier so that the catheter needle does not pierce theballoon material (needle stop mechanism), and provides compression suchthat the valve/septum re-seals after inflation and subsequent needlewithdrawal.

The concentric valve system can also provide radio opacity duringimplantation and is preferably titanium, gold, stainless steel, MP35N(nonmagnetic, nickel-cobalt-chromium-molybdenum alloy) or the like.Non-metallic polymeric materials can also be used, e.g., an acrylic,epoxy, polycarbonate, nylon, polyethylene, PEEK, ABS, or PVC or anythermoplastic elastomer or thermoplastic polyurethane that is fabricatedto be visible under x-ray (e.g., embedded with barium).

The septum is preferably cone shaped, so that the compressive forces aremaximized for self-sealing after inflation. The self-sealing septumallows air to be evacuated from the balloon for processing/compactingand insertion into the outer container, and allows for piercing by aninflation agent syringe needle (self-inflating configuration) orinflation catheter needle (inflatable configuration), and thensubsequent withdrawal of the inflation agent syringe needle ordetachment of the inflation catheter and withdrawal of the catheterneedle significantly limiting gas leakage outside of the balloon duringthe inflation process and needle withdrawal/catheter detachment. Theseptum is inserted into the valve using a mechanical fit mechanism toprovide compression. An additional ring can be placed at the distal endof the inner cylinder to provide additional compression to ensure theseptum material is dense enough to re-seal itself. The ring ispreferably metallic in nature, but can also be a non-metallic polymericmaterial such as an acrylic, epoxy, or thermoplastic elastomer orthermoplastic polyurethane. The ring material is preferably the samematerial as the cylinder, titanium, but can also be gold, stainlesssteel, MP35N or the like.

In the inflatable configuration, a larger, outer cylinder of theconcentric valve housing contains a slightly harder durometer materialthan the inner cylinder (50 Shore A or greater), but is also preferablysilicone. The purpose of using a harder durometer material is to ensuresealing when connected to the needle sleeve for inflation. The siliconelocated in the outer ring of the concentric valve is adhered to theballoon from the inside surface. The entire outer cylinder is filled anda small circular lip of this same material is provided that is slightlylarger than the diameter of the inner cylinder and extends to theoutside surface of the balloon. The lip is compatible with the bellshaped needle sleeve and provides sealing to enhance connection of thevalve to the catheter to withstand the inflation pressures applied andalso increases the tensile force of the catheter. This silicone lippreferably does not protrude past the balloon surface more than 2 mm toensure that the balloon surface remains relatively smooth and does notcause abrasion or ulcerations of the mucosa. It is designed to providecompressive forces against the needle sleeve of the catheter forinflation and detachment whereby when connected to the needle sleeve ofthe inflation catheters, the connection force during the inflationprocess can withstand up to 35 PSI. The seal is then broken duringdetachment using hydrostatic pressure that is more than 40 PSI less than200 PSI to break the connection force. Two additional retaining rings,preferably made of the same material as concentric valve, are includedin the valve system to further enhance the seal between the metal andthe valve silicone and provide additional mechanical support to ensureproper mechanical fit and are intended to disrupt slippage of thesilicone material from the hard (metallic) valve system (causing anincrease in tensile force).

The valve structure for the inflatable configuration uses a mechanicalfit mechanism to provide the functions of the self-sealable valve forinflation by the catheter and subsequent catheter detachment; however,primer and/or adhesive may be used to provide additional support inmaintaining the assembly. The configuration can be modified by modifyingthe surfaces of the metal components, making them more sticky orslippery to provide the desired mechanical/interference fit. Theinterference fit between the valve and the catheter can be modified tochange the pressure requirements for inflation and/or detachment.Additional assemblies can include overmolding the metallic portions orthe concentric system in silicone such that additional support rings toensure the mechanical fit and the tensile strength and forces requiredto sustain the assembly during catheter inflation and detachment can beomitted.

The total valve diameter in the inflatable configuration is designed tofit a miniature catheter system that does not exceed 8 French (2.7 mm,0.105 inches) in diameter. The total diameter does not exceed 1 inch(2.54 cm) and is preferably less than 0.5 inches (1.27 cm), tofacilitate swallowing. Additional valves can be added, if desired;however, it is generally preferred to employ a single valve so as tomaintain the volume of the deflated/folded balloon (and thus the outercontainer dimensions) as small as possible. The valve system ispreferably attached to the inner surface of the balloon such that ashear force greater than 9 lbs (40 N) is required to dislodge the valvesystem.

In a self-inflating configuration, the valve system can be attached tothe balloon (e.g., on its inside surface) without the use of an opening,orifice, or other conduit in the wall of the balloon. The valve systemcan utilize a septum with a durometer of 20 Shore A to 60 Shore D. Thevalve can be inserted or otherwise fabricated into a retaining structurethat has a higher durometer, e.g., 40 Shore D to 70 Shore D or more. Theretaining structure can be fabricated from a silicone, rubber, softplastic or any suitable non-metallic polymeric material such as anacrylic, an epoxy, a thermoplastic elastomer, or thermoplasticpolyurethane. Preferably, a structure, such as a ring, that can bemetallic or non-metallic but radioopaque (e.g., barium) and visibleunder X-ray, can be embedded in the retaining structure. Using amechanical fit mechanism of two structures of different durometers, onesofter (septum) with a large diameter, can be inserted into a snug, morerigid durometer structure creates compressive forces in the once openorifice to enable CO₂ retention and reduce susceptibility for CO₂ gasleaks. The metallic ring for radio-opacity also helps to createcompressive forces on the septum. The self-sealing septum allows air tobe evacuated from the balloon for processing/compacting and inserting inthe outer container, and also allows for the inflation agent to beinjected into the outer container for inflation initiation. Additionalseptums can be provided, if desired; however, it is generally preferredto employ a single septum so as to maintain the volume of thedeflated/folded balloon (and thus the outer capsule) as small aspossible. The valve system is preferably attached to the inner surfaceof the balloon such that a shear force greater than 9 lbs (40 N) isrequired to dislodge the valve system. A silicone head and opacity ringof a self-sealing valve system can be employed, as can a wedge-shapedseptum.

In the self-inflating configuration, an inoculation spacer is preferablyincorporated to guide a needle into the self-sealing valve for injectionof liquid activation agent into the lumen of the balloon and to preventthe needle from penetrating the wall of the deflated/folded balloonelsewhere such that pressure within the lumen of the balloon cannot bemaintained. The inoculation spacer also facilitates preventing liquidactivation agent from penetrating the inner container or the foldedballoon material, thereby focusing the activation agent in anappropriate manner to properly mix the reactants for CO₂ generationaccording to the criteria described above. The inoculation spacer isgenerally in the form of a tube or cylinder. The inoculation spacer ispreferably attached to the inner container and/or the self-sealing valvesystem with an adhesive or other fixing means; however, in certainembodiments the inoculation spacer can be “free-floating” and maintainedin position by the folding or rolling of the walls of the balloon. Theinoculation spacer can comprise any suitable material that can be passedafter separation, erosion, degradation, digestion, and/or dissolution ofthe outer container; however, preferable materials include non-metallicmaterials with a minimum Shore D durometer of 40 or more, any metallicmaterial, or a combination thereof. A cupped needle stop (inoculationspacer) can be employed in preferred embodiments.

Balloon

In a preferred embodiment, a self-inflating balloon is fully sealed 360degrees around. In the self-inflating configuration, with injection ofan inflation agent by needle syringe, there are preferably no externalopenings or orifices to the central lumen. In the inflatableconfiguration, a valve structure (either protruding, recessed, or flushwith the surface of the balloon) is provided for providing an inflationfluid to the central lumen. The balloon can have a “noninverted,”“inverted,” or “overlapped” configuration. In a “noninverted”configuration, the seams or welds and seam allowance, if any, are on theoutside of the inflated balloon. In an “overlapped” configuration,layers are overlapped, optionally with one or more folds, and secured toeach other via welds, a seam, adhesive, or the like, resulting in asmooth external surface. In an “inverted” configuration, the balloon hasa smooth external surface with seams, welds, adhesive bead, or the likeinside the inflated balloon. In order to create a balloon with aninverted configuration, e.g., a balloon with no external seam allowance(no wall material between the edge of the balloon and the weld, seam, orother feature joining the sides together), two balloon halves are joinedtogether in some fashion (e.g., adhered using adhesive or heat or thelike based on the balloon material used). One of the balloon halvesencompasses an opening to allow for the balloon to be pulled throughitself after adherence of the two halves and to have the seams of theballoon on the inside. The opening created is preferably circular butcan be any similar shape, and the diameter of the opening preferablydoes not exceed 3.8 cm; however, in certain embodiments a largerdiameter may be acceptable. A patch of material is adhered (adhesively,heat welded, or the like, based on the material used) to cover theoriginal balloon-half opening. The inversion hole thus created that issubsequently patched is small enough that the forces exerted duringinflation do not compromise the material used to maintain fluid in theballoon. The preferred shape for the inflated balloon in final assemblyis ellipsoid, preferably spheroid or oblate spheroid, with nominal radiiof from 1 inch (2.5 cm) to 3 inches (7.6 cm), a nominal height of from0.25 inches (0.6 cm) to 3 inches (7.6 cm), a volume of from 90 cm³ to350 cm³ (at 37° C. and at internal nominal pressure and/or fullinflation), an internal nominal pressure (at 37° C.) of 0 psi (0 Pa) to15 psi (103421 Pa), and a weight of less than 15 g. The self-inflatingballoon is configured for self-inflation with CO₂ and is configured toretain more than 75% of the original nominal volume for at least 25days, preferably for at least 90 days when residing in the stomach. Theinflatable balloon is configured for inflation with an appropriatemixture of gases so as to deliver a preselected volume profile over apreselected time period (including one or more of volume increaseperiods, volume decrease periods, or steady state volume periods).

The preferred shape for the inflated balloon in final assembly isellipsoid, preferably spheroid or oblate spheroid, with nominal radii offrom 1 inch (2.5 cm) to 3 inches (7.6 cm), a nominal height of from 0.25inches (0.6 cm) to 3 inches (7.6 cm), a volume of from 90 cm³ to 350 cm³(at 37° C. and at internal nominal pressure and/or full inflation), aninternal nominal pressure (at 37° C.) of 0 psi (0 Pa) to 15 psi (103421Pa), and a weight of less than 15 g. In certain embodiments wherein astable volume over the useful life of the device is preferred, theballoon is configured to maintain a volume of at least 90% to 110% ofits original nominal volume. In other embodiments, it can be desirablefor the balloon to increase and/or decrease in volume over its usefullife (e.g., in a linear fashion, in a stepwise fashion, or in anothernon-linear fashion).

Inner Container

The inner container for the self-inflating balloon is contained withinthe lumen of the balloon and contains the CO₂ generator for balloonself-inflation. The CO₂ generator comprises an inflation agent mixturehoused within the container. Preferably, from about 10% to about 80% ofthe total inflation agent used comprises powdered citric acid, with theremainder comprising powdered sodium bicarbonate. Sufficient inflationagent is provided such that upon completion of the CO₂ generatingreaction, the balloon achieves inflation at the nominal inflationpressure described above. Preferably, a total of from about 0.28 to 4grams inflation agent mixture is employed, depending upon the balloonsize to be inflated; preferably up to 1.15 grams of sodium bicarbonateis used with the remainder being powdered citric acid to generate 300cm³ of CO₂ at nominal pressure.

Inflation Assembly

An intragastric balloon system that is manually inflated by a miniaturecatheter can be employed in certain embodiments. The system preferablyremains “swallowable.” The balloon for delivery is in a compacted stateand is attached to a flexible, miniature catheter, preferably no largerthan 4 French (1.35 mm) in diameter. The catheter is designed such thata portion of the catheter can be bundled or wrapped upon itself fordelivery with the encapsulated balloon, allowing the patient to swallowboth catheter and balloon for delivery to the stomach. The balloon cancontain a self-sealable valve system for attachment of the catheter andinflation of the balloon once it reaches the stomach cavity. Theproximal end of the catheter can be left just outside of the patient'smouth, permitting connection to an inflation fluid container that canhouse the preferred inflation fluid (gas or liquid). After inflation thecatheter can be detached from the balloon valve and pulled back throughthe mouth. This method allows for the intragastric balloon to maintainits swallowability but allow for inflation by a fluid source or amixture of fluid sources via the catheter. Alternatively, a more rigid,pushable system can be employed wherein the balloon valve is compatiblewith either the swallowable, flexible catheter or the pushable, rigidcatheter assembly.

The inflation catheters (swallowable or administrator-assisted pushable)described herein are configured to deliver the balloon device orally andwithout any additional tools. The administration procedure does notrequire conscious sedation or other similar sedation procedures orrequire endoscopy tools for delivery. However, other versions of thedevice can be used in conjunction with endoscopy tools for visualizationor can be adapted such that the balloon device can be deliverednasogastrically as well.

In operation, the proximal end of the inflation catheter is connected toa valve or connector that allows for connection to the inflation sourceor the disconnect source, this is preferably a Y-arm connector orinflation valve. The connector materials may consist of polycarbonate orthe like and can connect to a single or multi-lumen catheter tube. Thedistal end of the inflation catheter is connected to the universalballoon valve of the balloon that has been compacted and housed within agelatin capsule or compacted using gelatin bands. The catheter tube ispreferably from 1 French (0.33 mm) to 6 French (2 mm) in diameter. Thecatheter is preferably long enough to extend out past the mouth(connected to the inflation connector or valve) and transverse theesophagus down to at least the middle of the stomach—approximately 50-60cm. Measurement ticks can be added to the tubing or catheter to aid inidentifying where the end of the tube is located. Timing for inflationcan be initiated by having the tube contain a pH sensor that determinesa location difference between the esophagus (pH 5-7) and the stomach (pH1-4) based on the different pH between the two anatomical sources, orcan be derived or verified from the expected pressure in a contained(i.e., esophagus) versus a less-constrained space (i.e., stomach). Thetube can also contain nitinol that has a tunable transmission to thebody temperature, taking into account the timing for swallowing. Thetube can also be connected to a series of encapsulated or compactedballoons on a single catheter. Each can be inflated and releasedseparately. The number of balloons released can be tune-able to thepatient's needs and desired weight loss.

In certain embodiments, a catheter with the balloon at the distal end(inflated with air) is employed to temporarily and firmly hold theballoon in place. A small deflated balloon catheter can be positionedthrough the head of the gastric balloon (e.g., a “balloon within theballoon”), and then inflated with air during delivery to firmly hold thecapsule and balloon in place and prevent spontaneous detachment ofballoon from the catheter. This balloon catheter can incorporate a dualchannel that can also allow the bigger gastric balloon to be inflated(by gas or liquid). Once the gastric balloon has been satisfactorilyinflated, the small air balloon catheter can be deflated and pulled outof the valve (allowing the valve to self seal), and out of the body,leaving the inflated gastric balloon in the stomach.

In other embodiments, the catheter may be coated to enhanceswallowability or is impregnated or treated with one or more localanesthetics or analgesics to ease swallowing. Such anesthetics mayinclude anesthetics in the amino amide group, such as articaine,lidocaine and trimecaine, and anesthetics in the amino ester group, suchas benzocaine, procaine and tetracaine. Such analgesics may includechloraseptic.

Dual Lumen Catheter

In a preferred embodiment, a swallowable dual lumen catheter isprovided. The dual lumen catheter has two lumens with a diameter of thecomplete assembly no larger than 5 French (1.67 mm), preferably nolarger than 4 French (1.35 mm). The inner lumen preferably does notexceed 3 French (1 mm) and functions as the inflation tube, and theouter lumen preferably does not exceed 5 French (1.67 mm) and functionsas the disconnection tube; the inner and outer lumen do not exceed 2French (0.66 mm) and 4 French (1.35 mm), in diameter, respectively. Thecatheter assembly is connected to a needle assembly, described in moredetail below, at the distal end and to a dual port inflation connectorat the proximal end. The tubing that the catheter assembly employs isflexible for swallowability, is kink resistant, can withstand bodytemperature, is resistant to acid, and is biocompatible as the tubetransverses the alimentary canal into the stomach cavity. The tubematerials are preferably soft and flexible and have moderate tensilestrength and a significant amount of hoop strength to handle appliedpressures. The lumens are preferably round and co-axial andfree-floating so as to provide flexibility. The dual lumen assembly alsopreferably requires no adhesive or glue. Alternative lumenconfigurations can include two D-lumens or a combination of a D-lumenand round lumen, and can be used in stiffer configurations of the finalcatheter assembly. Preferred materials for the tubing include athermo-resistant polyethylene tubing such as PEBAX® or athermo-resistant polyurethane tubing such as PELLETHANE™, PEEK or Nylon.The tubing can also be manufactured out of bioresorbable materials suchas polylactic acid (PLA), poly-L-aspartic acid (PLAA),polylactic/glycolic acid (PLG), polycaprolactone (PCL),DL-lactide-co-ε-caprolactone (DL-PLCL) or the like, wherein the tube canbe released after inflation and detachment and swallowed as normal.

At the distal end of the catheter assembly, the inner lumen or inflationtube is attached to the needle assembly that is used to puncture theballoon's self-sealing valve, preferably located at one of the apexes ofthe balloon housed inside of a gelatin capsule as outer container. Theouter lumen is connected to the needle sleeve and provides connectionforce between the catheter assembly and balloon providing the tensilestrength to withstand balloon inflation pressures, e.g., pressures of upto 10 psi or higher, while maintaining the assembly together. The needlesleeve is configured to mechanically couple with the balloon valveassembly. The needle is preferably made of metal, preferably stainlesssteel or the like, with a maximum size of 25 gauge (0.455 mm),preferably no smaller than 30 gauge (0.255 mm) for inflation timingpurposes. The needle sleeve is preferably a soft material such as nylonor the like, or can also be polycarbonate, polyethylene, PEEK, ABS orPVC. The needle sleeve covers the length of the needle in its entirety,such that the body is protected from the needle and the needle can onlypierce the balloon septum. Preferably the needle sleeve is flush orextends out slightly more than the needle length. The needle is insertedinto the balloon septum prior to swallowing and maintains a retentionforce of approximately 0.33 lb (0.15 kg) when coupled to the siliconearea of the balloon valve. The needle sleeve is preferably slightly bellshaped or contains a circular relief or lip so that when inserted intothe silicone area of the valve a lock and key mechanism is created toincrease the tensile strength of the assembly and enhance the sealingfor inflation.

At the proximal end, the catheter assembly is connected to a Y-adapterassembly preferably made of polycarbonate. The y-adapter is “keyed” sothat the inflation gas and connection fluid are connected to thecatheter assembly appropriately and travel down the correct lumen.

Prior to inflation, priming of the disconnection lumen may be employedusing a liquid. For example, the outer lumen is first flushed with 2 ccof water, saline, DI water or the like prior to balloon inflation.Thereafter, the inflation source container is attached to the connectorleading to the inner lumen. The inflation source container works on thepremise of the ideal gas law and a pressure decay model. For a givencompressed gas formulation, the device is designed to equalize such thata higher starting pressure is used to inflate the balloon than is theresulting end pressure of the balloon. The starting pressure and volumeare dependent upon the gas formulation selected, as well as the lengthof the catheter and the starting temperature (typically ambienttemperature) and ending temperature (typically body temperature).

After inflation, the balloon is detached from the catheter assemblyusing hydraulic pressure. A syringe filled with water, DI water, orpreferably saline is attached to the female end of the Y-assembly. Thesyringe contains 2 cc of liquid and when the syringe plunger is pushedin, enough hydraulic pressure is exerted such that the needle is ejectedfrom the balloon valve.

Single Lumen Catheter

To further reduce the diameter of the inflation catheter, therebyincreasing swallowability comfort, a single lumen catheter can beemployed that does not exceed 2 French (0.66 mm) in diameter.

The needle/needle sleeve assembly is similar in design to that of thedual lumen catheter described herein. However, with the single lumensystem, the distal end of the catheter lumen connects to the needlesleeve only and there is no second catheter inside. Instead, a singlethread attached to a needle hub runs co-axially the length of thecatheter to aid in tensile strength for detachment and overallflexibility.

The needle sleeve is slightly bell shaped or contains a circular reliefor lip so that when inserted into the silicone area of the valve a lockand key mechanism is created to increase the tensile strength of theassembly, enhance the sealing for inflation, and since this is a singlelumen assembly, the lip increases the force required to remove theneedle from the valve so this does not occur haphazardly during theinflation process.

The proximal end of the catheter is connected to a 3-way valve and usesa method of exclusion for inflation and detachment of the balloon. Thedistal end of the catheter contains the needle sleeve, which is made ofnylon or other similar source. The needle is metallic and preferablystainless steel.

The tubing that the catheter assembly employs is flexible forswallowability, is kink resistant, can withstand body temperature, isresistant to acid, and is biocompatible as the tube transverses thealimentary canal into the stomach cavity. The tube materials arepreferably soft and flexible, preferably co-axial, and resistant tonecking or buckling or kinking. For a single lumen system, the cathetertubing is preferably made of PEBAX®, but can also comprise bioresorbablematerials such as PLA, PLAA, PLG, PCL, DL-PLCL or the like, wherein thetube can be released after inflation and detachment and swallowed asnormal. The wire inside the catheter tubing attached to the needle ispreferably a nylon monofilament, but Kevlar or nitinol wire or othersuitable materials can also be used.

To inflate the balloon, the distal end of the catheter is attached tothe balloon capsule where the needle protrudes through the self-sealablevalve. The container is swallowed and a portion of the inflationcatheter remains outside of the mouth. The inflation source container isconnected to the proximal 3-way valve, where the port for inflation gasis chosen by excluding the other ports. The inflation fluid (preferablycompressed nitrogen gas or a mixture of gases) travels down the singlecatheter lumen, whereby the inflation gas selects the path of leastresistance, or more specifically through the needle cavity and into theballoon. The balloon is preferably inflated in less than 3 minutes.

To detach and withdraw the needle from the balloon valve, 2 cc or othersuitable volume of water or other liquid is injected into the catheterat a high pressure. Since water has a high surface tension andviscosity, it occludes the needle pathway and the pressure istransferred to the outside needle sleeve, thereby breaking the fitbetween the needle sleeve and the balloon valve.

If it is desired to place a substance inside the balloon, such as wateror acid or any alternative liquid, it can be done by using a lowerpressure to inject the liquid.

Miniature Stiff-Bodied Inflation Catheter

In certain embodiments, a stiff-bodied inflation catheter can beemployed, which can be placed orally or trans-nasally. This system canbe from 1 French (0.33 mm) to 10 French (3.3 mm), preferably 8 French(2.7 mm) in diameter. A larger diameter is typically preferred toenhance pushability, with wall thickness also contributing topushability and kink resistance. The length of the tube can beapproximately 50-60 cm. As discussed above, measurement ticks can beadded to the tubing to identify where the end of the tube is located, ora pH or pressure sensor on the catheter can be employed to detectlocation of the balloon.

This system for inflation/detachment is similar to the dual lumen systemdescribed above, but with a larger needle sleeve to accommodate thelarger diameter tube. Materials that can be used in the lumen include,e.g., expanded polytetrafluoroethylene (EPTFE) for the outer lumen andpolyetheretherketone (PEEK) for the inner lumen. To also enhancepushability, a strain relief device can be added to the distal andproximal ends. It is particularly preferred to have strain relief at thedistal end, e.g., 1 to 8 inches, preferably 6 inches, to ensure thecatheter bypasses the larynx and follows into the esophagus. Theproximal end can have strain relief as well, e.g., to ensure fit of theY-arm. The preferred material for the strain relief is a polyolefin. Themethod for inflation/detachment is the same method as for the dual lumenconfiguration where the outer lumen connects to the needle sleeve andthe inner lumen connects to the needle. As part of the procedure, thepatient can swallow water or other suitable liquid so as to distendesophageal tissue for smooth passage down of the device. Patients canalso be administered an anesthetic at the back of the throat to numb thearea and lessen the gag reflex.

The tube can also be connected to a series of encapsulated or compactedballoons on a single catheter such that a total volume of up to 1000 ccor more can be administered, as necessary. Each can be inflated andreleased separately. The number of balloons released can be tunable tothe patient's needs and desired weight loss.

In addition, a catheter can be used for administering a gastric balloonthat is similar to balloon catheters used in angioplasty termed“over-the-wire” or rapid exchange catheters. In this case where thepatients attempts to swallow the catheter but fails so the stiffcatheter—or physician assisted catheter can slide over the flexiblecatheter and the balloon can be pushed down in the same manner as thephysician-assisted catheter. Different materials can be used to providethe varying degrees of flexibility or one material that is fabricatedwith different diameters across the length to vary the degree ofstiffness can be used.

The swallowable self-inflating balloon construction method and theswallowable inflation tube construction method both remove therequirement for endoscopy to place the balloon and make the balloonadministration process less invasive. This also allows for the totalvolume to be placed in a patient to be “titratable,” or adjustable. Whena balloon is placed for 30 days, a patient may report that over timethey lose their feeling of fullness without eating. To compensate,another balloon can be placed easily without sedation and endoscopy.When a non-deflatable balloon is to be removed endoscopically, it isdesirable to color-code the balloon composite walls with differentcolors so that the physician has a visual marker for removing theballoon at the end of its useful life while keeping the balloon that hasremaining useful life in the patient's stomach.

In addition, the balloon wall can be marked approximately 180° from theself-sealing valve such that when the balloon is puncturedendoscopically it folds more efficiently on itself so as to facilitateremoval of the thin-walled structure without causing esophagealperforations and/or other damage by the balloon due to its shape,stiffness, and/or thickness of the wall material.

Inflation Fluid Container

The inflation fluid container is employed to control the amount orvolume of fluid placed inside of the balloon. This can be in the form ofa canister of, e.g., PVC, stainless steel, or other suitable material.The container can also be in syringe form. The materials employed areable contain a fluid, preferably in gas form, e.g., compressed ornon-compressed N₂, Ar, O₂, CO₂, or mixture(s) thereof, or compressed ornon-compressed atmospheric air (a mixture of N₂, O₂, Ar, CO₂, Ne, CH₄,He, Kr, H₂, and Xe). The balloon composite wall materials and respectivediffusion gradients and gas permeability characteristics are used toselect a fluid for inflation of the intragastric balloon, so as toprovide a desired volume profile over time for the inflated balloon. Theinflation fluid container materials are selected to ensure no or minimaldiffusion or leakage of the fluid before it is connected to the y-armconnector or valve of the inflation catheter. The inflation fluidcontainer preferably incorporates a pressure gauge and a connector. Itcan also contain a smart chip that notifies the healthcare professionalof whether inflation is successful or if the balloon should be detacheddue to an error in the system.

To maintain “swallowability” of the balloon and to ensure comfort of thepatient during the procedure, it is preferred to minimize the amount oftime the catheter is placed in the mouth/esophagus. Timing of inflationis can be selected so as to minimize time in place. The outercontainer-catheter assembly, once swallowed, takes approximately 4-8seconds to reach the stomach. Once in the stomach, the Inflation sourcecontainer can be attached to the valve or port of catheter system.Inflation timing can be controlled by selecting the length of catheter,diameter of the catheter tube, the starting temperature, and thestarting pressure. Using the Ideal Gas Law for nitrogen and Boyle's Law(P₁V₁=P₂V₂) the amount of starting volume/pressure can be derived, wheretemperature is controlled inside the inflation source container to matchthat of the body. It is desired to have an inflation time after swallowof less than 5 minutes, and preferably 2-3 minutes, before balloondetachment and catheter withdrawal. The inputs use to derive inflationof the balloon (preferably in less than 3 minutes) include inflationcontainer volume, type of inflation fluid (preferably a compressed gasor compressed gas mixture), starting pressure, catheter length anddiameter, and desired end volume and pressure of the balloon. Thus, dueto differences in diameter, a 2 French catheter system requires a higherstarting pressure to achieve the same target balloon volume and pressurein the same time frame, assuming use of the same compressed gasformulation. In general, it is understood that starting with a higherpressure with the same flow rate/volume can decrease the inflation time.

The inflation source container provides feedback to the end user basedon a pressure decay system. Where there is an expected starting pressureand expected ending pressure to indicate whether the balloon is inflatedproperly, there is no need for endoscopic visualization. Each scenarioof expected pressure outputs can have its own tolerances around it toreduce possibilities of false positives, and the inflation fluidcontainer can provide feedback based on these tolerances as to thestatus of balloon inflation and detachment. This is derived based on theIdeal Gas Law, where there is an expected end pressure based on thefixed volume of the balloon. If the pressure remains high and doesn'tdecay as expected, this can indicate a failure in the system (e.g., theballoon container did not dissolve, the balloon is expanding in theesophagus because there is, e.g., a kink in the tube or other failure inthe catheter system). For example, for a successful decay using nitrogenonly as the inflation fluid, the starting pressure is 22 PSI to inflatea balloon to 250 cc and 1.7 psi (0.120 kg/cm²) for a nylon-basedmaterial. To indicate successful balloon inflation, a math chip can beadded to the inflation source container that provides at least one of avisual, audible, or tactile notification, or otherwise transmits anotification to a healthcare professional or administrator of whetherinflation is successful or if there is an error in the system based onthe pressure curve and a set of predetermined pressure tolerances andexpected timing of inflation.

Another method for detection of any degree of constraint that theballoon may be experiencing (e.g., capsule dissolved but balloon is inthe esophagus or duodenum, or balloon is in the stomach and the capsulehas not dissolved by reading the gauge output is to employ an inflationcanister that has at least two reservoirs (one large and one small) andat least two gauges, with one or more valves that allow for selection ofgas release into the second reservoir or into the balloon itself. Withtwo reservoirs, the larger reservoir can contain the total amount offluid required to fill the balloon. A small amount of fluid can bereleased from the larger reservoir into the smaller reservoir first todetermine the location of the balloon and its readiness for fullinflation. If the small amount of fluid in the smaller reservoir isreleased into the balloon catheter and the feedback on the gauge of thesmaller reservoir indicates that the pressure is high, this indicatesthat the balloon is still contained in the capsule and it is not readyto be inflated. When the gauge reads back a medium pressure level (e.g.,1-4 psi), this indicates that the balloon is in a constrained space,such as the esophagus or duodenum, and should not be inflated. When theballoon catheter's feedback as read on the gauge is approximately 1 psi,this indicates that the balloon is in the stomach and ready to beinflated. If the feedback is at 0 psi, this indicates is a leak in theballoon valve catheter system and that the device should be retrieved.Once the balloon is detected in the stomach space, then the largerreservoir is opened and the balloon is inflated to its desired pressure.

Alternatively, the balloon can be filled based on a starting pressure byusing a spring mechanism, a balloon-within-balloon mechanism, or otherpressure source. These mechanisms can potentially result in morepredictable/consistent pressure decay curves, and again can haveaccompanying, predetermined tolerances for feedback back to the enduser.

Composite Wall

The materials selected for the composite wall of the balloon may beoptimized to maintain the original inflation gas without significantdiffusion, or may also allow for diffusion of the gases located in thegastric environment, e.g., CO₂, O₂, argon, or N₂ to diffuse through thewall of the balloon to inflate, partially or wholly, once the balloon isplaced in the stomach. A fluid (a liquid or gas) can also be addedinside of the balloon using the inflation catheter(s) described hereinto change diffusion direction of the balloon composite wall and when itreaches stasis based on the internal and external environment.

A gastric balloon inflated by nitrogen, CO₂ gas, SF₆, a single fluid(liquid or gas) or a mixture of fluids employs a composite wall thatprovides barrier properties (fluid retention), properties impartingresistance to pH and moisture conditions in the gastric environment orthe environment within the central lumen of the balloon, and structuralproperties to resist gastric motility forces, abrasion of the balloonwall in vivo, and damage during manufacturing and folding of theballoon. Certain materials employed in the balloon materials are able towithstand a hostile gastric environment designed to break down foreignobjects (e.g., food particles). Some of the variables that the gastricenvironment encompasses are as follows: gastric liquid pH of from 1.5-5;temperature of approx. 37° C.; a relative humidity of 90-100%; ingressof gastric space gas content; and constant gastric motility externalpressures of from 0-4 psi at variable frequencies and cycle times basedon the fed state of the stomach. The external pressure imparted bygastric motility can also cause abrasions on the surface of the balloon.The inside of the balloon lumen may contain moisture from a solutioninjected in the balloon for timing of auto-deflation or any moisturethat has transferred across the membrane due to the external humidenvironment. In addition to these environmental stresses the wallmaterials meet biocompatibility requirements and are constructed suchthat the total thickness of the wall (barrier material) is thin enoughto be compacted and placed inside of a swallowable-sized container(“outer container”) without significant damage or lodging. The outercontainer is small enough to transcend the esophagus (which has adiameter of approximately 2.5 cm). The wall or barrier material is alsoheat formable and sealable for balloon construct and maintains a bondstrength that can contain internal gas pressures of up to 10 psigenerated by the initial inflation pressure as well as pressure due tothe ingress of gas molecules from the stomach cavity until the system'sgas environment reaches stasis. The film properties that are evaluatedto determine suitability for use in the composite wall of the ballooninclude pH resistance, water vapor transmission rate, gas barrierproperties, mechanical strength/abrasion properties, temperatureresistance, formability, flex-crack (Gelbo) resistance, surface energy(wetability) compliance, and heat bond potential.

The various layers in the composite wall can impart one or moredesirable properties to the balloon (e.g., CO₂ retention, resistance tomoisture, resistance to acidic environment, wetability for processing,and structural strength). A list of polymer resins and coatings that canbe combined into a multi-layer preformed system (“composite wall”) isprovided in Tables 1a-b. These films can be adhesively bonded together,co-extruded, or adhered via tie layers or a combination thereof toobtain the desired combination of properties for the composite wall, asdiscussed below. The materials identified as film coatings in Tables1a-b are provided as coatings applied to a base polymer film, e.g., PET,Nylon, or other structural layer.

TABLE 1a Film Resins Characteristics Good Structural/ Behavior/ GoodFluid Good Mechanical Retention Manufacturability/ Strength/ BarrierSurface Compliance Properties Energy Properties FILM RESINS PolyethyleneX X Terephthalate (PET) Polytrimethylene Terephthalate (PTT) LiquidCrystal X X Polymer (LCP) Polytrimethylene X X naphthalate (PTN)Polyethylene X X naphthalate (PEN) Polyimide (PI) X X Linear Low DensityX Polyethylene (LLDPE) Ethylene Vinyl X Alcohol (EVOH) Polyamide: NylonX X (PA) and Nylon-6 (PAG)/Nylon 12 High Density X Polyethylene (HDPE)Polypropylene (PP) X Polyurethane X PVDC (Saran) X X Polyether Block XAmide (Pebax) Polyvinyl Alcohol X (PVOH) Silicone X X

TABLE 1b Film Coatings Characteristics Good Structural/ Behavior/ GoodFluid Good Mechanical Retention Manufacturability/ Strength/ BarrierSurface Compliance Properties Energy Properties FILM COATINGS SiliconeDioxide X (SiO2) Aluminum Oxide X (Al₂O₃) Nanopolymers X (Nano/Clay)External Organic X Coatings (e.g., epoxy amine) Inorganic Coatings X(e.g., Amorphous Carbon) Oxygen Scavengers X Parylene C X

Fluid Retention Layers

In preferred embodiments, a blended polymer resin using multiple layersis employed to maintain the inflated balloon's shape and volume byretaining the inflation fluid for the duration of the intended use.Certain barrier films, widely used in the food packaging and plasticbottling industries, can advantageously be employed for this purpose inthe composite wall of the balloon. Preferably, the barrier materialshave a low permeability to carbon dioxide (or other gases, liquids, orfluids that are alternatively or additionally used to inflate thevolume-occupying subcomponent). These barrier layers preferably havegood adherence to the base material. Preferred barrier coating materialsand films include polyethylene terephthalate (PET), linear low densitypolyethylene (LLDPE), ethylene vinyl alcohol (EVOH), polyamides such asNylon (PA) and Nylon-6 (PA-6), polyimide (PI), liquid crystal polymer(LCP), high density polyethylene (HDPE), polypropylene (PP),biocompatible poly(hydroxyamino ethers), polyethylene naphthalate,polyvinylidene chloride (PVDC), saran, ethylene vinyl alcoholcopolymers, polyvinyl acetate, silicon oxide (SiOx), silicon dioxide(SiO₂), aluminum oxide (Al₂O₃), polyvinyl alcohol (PVOH), nanopolymers(e.g., nanoclay), polyimide thermoset film, EVALCA EVAL EF-XL, HostaphanGN, Hostaphan RHBY, RHB MI, Techbarrier HX (SiOx-coated PET), TriadSilver (silver metalized PET), Oxyshield 2454, Bicor 84 AOH,acrylonitrile copolymers, and copolymers of terephthalic acid andisophthalic acid with ethylene glycol and at least one diol. Alternativegas-barrier materials include polyamine-polyepoxides. These materialsare typically provided as a solvent-based or aqueous-based thermosettingcomposition and are typically spray-coated onto a preform and thenheat-cured to form the finished barrier coating. Alternative gas barriermaterials that can be applied as coatings to the volume-occupyingsubcomponent include metals such as silver or aluminum. Other materialsthat may be used to improve the gas impermeability of the volumeoccupying subcomponent include, but are not limited to, gold or anynoble metal, PET coated with saran, and conformal coatings.

One method that is used in the packaging industry to delay diffusion ofthe inflation fluid is to thicken the material. Thickening the materialis generally not preferred, as the total composite wall thicknesspreferably does not exceed 0.004 inches (0.010 cm) in order for theballoon to be foldable into the desired delivery container size forswallowing by a patient.

A multilayer polymer film that is able to withstand the gastricenvironment over the course of the usable life of the balloon includeslinear low density polyethylene (LLDPE) adhesively bonded to a Nylon 12film. Alternatively, an additional film layer with barrier properties,such as PVDC can be added to the composite wall.

The layers providing gas barrier properties are preferably situated asinner layers in the composite wall as they are less mechanically robustthan resins that are considered “structural” such as Nylon and the like.

Structural Layers

Layers such as polyurethane, Nylon, or polyethylene terephthalate (PET)can be added to the composite wall for structural purposes, and arepreferably placed as outermost (proximal to the gastric environment orproximal to the central lumen of the balloon) layers, provided that thepH resistance of such layers can withstand the acidic environment of thestomach or the central lumen of the balloon.

Layer Chemistry Polyethylene Terephthalate (PET)

Polyethylene terephthalate is a thermoplastic polymer resin of thepolyester family. Polyethylene terephthalate may exist as an amorphous(transparent) or as a semi-crystalline material. The semi-crystallinematerial can appear transparent (spherulites <500 nm) or opaque andwhite (spherulites up to a size of some μm) depending on its crystalstructure and spherulite size. Its monomer (bis-ß-hydroxyterephthalate)can be synthesized by the esterification reaction between terephthalicacid and ethylene glycol with water as a byproduct, or bytransesterification reaction between ethylene glycol and dimethylterephthalate with methanol as a byproduct. Polymerization is through apolycondensation reaction of the monomers (done immediately afteresterification/transesterification) with ethylene glycol as thebyproduct (the ethylene glycol is directly recycled in production). Someof the trade names of PET products are Dacron, Diolen, Tergal, Terylene,and Trevira fibers, Cleartuf, Eastman PET and Polyclear bottle resins,Hostaphan, Melinex, and Mylar films, and Arnite, Ertalyte, Impet, Ryniteand Valox injection molding resins.

PET consists of polymerized units of the monomer ethylene terephthalate,with repeating C₁₀H₈O₄ units. PET can be semi-rigid to rigid, dependingon its thickness, and is very lightweight. It makes a good gas and fairmoisture barrier, as well as a good barrier to alcohol and solvents. Itis strong and impact-resistant. It is naturally colorless with hightransparency.

When produced as a thin film (biaxially oriented PET film, often knownby one of its trade names, “Mylar”), PET can be aluminized byevaporating a thin film of metal onto it to reduce its permeability, andto make it reflective and opaque (MPET). These properties are useful inmany applications, including flexible food packaging. When filled withglass particles or fibers, it becomes significantly stiffer and moredurable. This glass-filled plastic, in a semi-crystalline formulation,is sold under the trade name Rynite, Arnite, Hostadur, and Crastin.

One of the most important characteristics of PET is intrinsic viscosity.The intrinsic viscosity of the material, measured in deciliters per gram(dl/g) is dependent upon the length of its polymer chains. The longerthe chains, the stiffer the material, and therefore the higher theintrinsic viscosity. The average chain length of a particular batch ofresin can be controlled during polymerization. An intrinsic viscosity ofabout: 0.65 dl/g-0.84 dl/g is preferred for use in a composite wall.

In addition to pure (homopolymer) PET, PET modified by copolymerizationis also available. In some cases, the modified properties of copolymerare more desirable for a particular application. For example,cyclohexane dimethanol (CHDM) can be added to the polymer backbone inplace of ethylene glycol. Since this building block is much larger (6additional carbon atoms) than the ethylene glycol unit it replaces, itdoes not fit in with the neighboring chains the way an ethylene glycolunit can. This interferes with crystallization and lowers the polymer'smelting temperature. Such PET is generally known as PETG (EastmanChemical and SK Chemicals are the only two manufacturers). PETG is aclear amorphous thermoplastic that can be injection molded or sheetextruded. It can be colored during processing. Another common modifieris isophthalic acid, replacing some of the 1,4-(para-) linkedterephthalate units. The 1,2-(ortho-) or 1,3-(meta-) linkage produces anangle in the chain, which also disturbs crystallinity. Such copolymersare advantageous for certain molding applications, such asthermoforming. On the other hand, crystallization is important in otherapplications where mechanical and dimensional stability are important.For PET bottles, the use of small amounts of CHDM or other comonomerscan be useful: if only small amounts of comonomers are used,crystallization is slowed but not prevented entirely. As a result,bottles are obtainable via stretch blow molding (“SBM”), which are bothclear and crystalline enough to be an adequate barrier to aromas andgases such as carbon dioxide in carbonated beverages.

Crystallization occurs when polymer chains fold up on themselves in arepeating, symmetrical pattern. Long polymer chains tend to becomeentangled on themselves, which prevents full crystallization in all butthe most carefully controlled circumstances. 60% crystallization is theupper limit for commercial products, with the exception of polyesterfibers.

PET in its natural state is a crystalline resin. Clear products can beproduced by rapidly cooling molten polymer to form an amorphous solidLike glass, amorphous PET forms when its molecules are not given enoughtime to arrange themselves in an orderly fashion as the melt is cooled.At room temperature the molecules are frozen in place, but if enoughheat energy is put back into them, they begin to move again, allowingcrystals to nucleate and grow. This procedure is known as solid-statecrystallization.

Like most materials, PET tends to produce many small crystallites whencrystallized from an amorphous solid, rather than forming one largesingle crystal. Light tends to scatter as it crosses the boundariesbetween crystallites and the amorphous regions between them. Thisscattering means that crystalline PET is opaque and white in most cases.Fiber drawing is among the few industrial processes that produces anearly single-crystal product.

Comonomers such as CHDM or isophthalic acid lower the meltingtemperature and reduces the degree of crystallinity of PET (especiallyimportant when the material is used for bottle manufacturing). Thus theresin can be plastically formed at lower temperatures and/or with lowerforce. This helps to prevent degradation, reducing the acetaldehydecontent of the finished product to an acceptable (that is, unnoticeable)level. Other ways to improve the stability of the polymer is by usingstabilizers, mainly antioxidants such as phosphites. Recently, molecularlevel stabilization of the material using nanostructured chemicals hasalso been considered.

Unreinforced PET has the following properties: Bulk Density 0.800-0.931g/cc; Density 1.10-1.20 g/cc @Temperature 285-285° C.; 1.25-1.91 g/cc;Apparent Bulk Density 0.000850 g/cc; Water Absorption 0.0500-0.800%;Moisture Absorption at Equilibrium 0.200-0.300%; Water Absorption atSaturation 0.400-0.500%; Particle Size 2500 μm; Water Vapor Transmission0.490-6.00 g/m²/day; Oxygen Transmission 5.10-23.0 cc-mm/mg-24 hr-atm;Viscosity Measurement 0.550-0.980; Viscosity Test 74.0-86.0 cm³/g;Thickness 250-254 microns; Linear Mold Shrinkage 0.00100-0.0200 cm/cm;Linear Mold Shrinkage, Transverse 0.00200-0.0110 cm/cm; Hardness,Rockwell M 80.0-95.0; Hardness, Rockwell R 105-120 105-120; BallIndentation Hardness 160-170 MPa; Tensile Strength, Ultimate 22.0-207MPa; Film Tensile Strength at Yield, MD 55.0-59.0 MPa; Film TensileStrength at Yield, TD 53.0-57.0 MPa; Film Elongation at Break, MD40.0-600%; Film Elongation at Break, TD 200-600%; Film Elongation atYield, MD 4.00-6.00%; Film Elongation at Yield, TD 4.00-6.00%; TensileStrength, Yield 47.0-90.0 MPa; Elongation at Break 1.50-600%; Elongationat Yield 3.50-30.0%; Modulus of Elasticity 1.83-14.0 GPa; FlexuralModulus 1.90-15.2 GPa; Flexural Yield Strength 55.0-240 MPa; CompressiveYield Strength 20.0-123 MPa; Izod Impact, Unnotched 2.67 J/cm-NB; IzodImpact, Unnotched Low Temp (ISO) 160-181 kJ/m²; Izod Impact, Notched,Low Temp (ISO) 3.10-4.20 kJ/m²; Charpy Impact Unnotched 3.00 J/cm²-NB;Charpy Impact, Notched, Low Temp 0.270-0.500 J/cm²; Charpy Impact,Notched 0.200-1.40 J/cm²; Impact Test 0.800-8.20 J @Temperature −40.0°C.; Coefficient of Friction 0.190-0.250; Tear Strength, Total 15.0-120N; Elmendorf Tear Strength, MD 3.14-4.00 g/micron; Elmendorf TearStrength, TD 3.24-5.20 g/micron; Dart Drop 1.08-2.00 g/micron; TaberAbrasion, mg/1000 Cycles; Film Tensile Strength at Break, MD 13.8-60.0MPa; Film Tensile Strength at Break, TD 39.0-48.0 MPa; Izod Impact,Notched @-40° C. 0.270-0.630 J/cm; Izod Impact, Notched 0.139-100 J/cm;Izod Impact, Notched (ISO) 2.00-10.0 kJ/m²; Electrical Resistivity5.00e+6-1.00e+16 ohm-cm; Surface Resistance 1.00e+14−1.00e+16 ohm;Dielectric Constant 2.40-3.90; Dielectric Strength 15.7-60.0 kV/mm;Dissipation Factor 0.00100-0.0250; Arc Resistance 80.0-181 sec;Comparative Tracking Index 175-600 V; Heat of Fusion 56.0-65.0 J/g; CTE,linear 25.0-92.0 μm/m-° C.; CTE, linear, Transverse to Flow 48.0-80.0μm/m-° C.; Specific Heat Capacity 1.10-1.20 J/g-° C.; 1.30-2.30 J/g-° C.@Temperature 60.0-280° C.; Thermal Conductivity 0.190-0.290 W/m-K;Melting Point 200-255° C.; Maximum Service Temperature, Air 100-225° C.;Deflection Temperature at 0.46 MPa (66 psi) 66.0-245° C.; DeflectionTemperature at 1.8 MPa (264 psi) 60.0-240° C.; Vicat Softening Point74.0-85.0° C.; Minimum Service Temperature, Air −20.0° C.; GlassTemperature 70.0-78.0° C.; UL RTI, Electrical 75.0-175° C.; Haze0.300-10.0%; Gloss 108-166%; Transmission, Visible 67.0-99.0%; GardnerColor Number −3.00-85.0; Processing Temperature 120-295° C.; MoldTemperature 10.0-163° C.; Drying Temperature 70.0-160° C.; Dry Time3.00-8.00 hour; Moisture Content 0.0100-0.400%; Injection Pressure68.9-120 MPa; Back Pressure 8.00-18.0 MPa.

Polyethylene terephthalate films are available from Mitsubishi PolyesterFilm of Wiesbaden, Germany under the trade name Hostaphan®. Hostaphan®GN is a glass clear biaxially oriented film, made of polyethyleneterephthalate (PET) and is characterized by its high transparency andsurface gloss and its low haze accompanied by its excellent mechanicalstrength and dimensional stability. Hostaphan® GN is one or two sidechemically treated for improved slip and processability as well as forimprovement of the adhesion of coatings, printing inks or metalliclayers. Hostaphan® RHBY is a biaxially oriented film made ofpolyethylene terephthalate (PET) with a structure optimized to offerpreviously unattainable barrier properties against oxygen, water vaporand other gases as well as aroma substances after vacuum coating withaluminum, Al₂O₃ or SiOx.

Linear Low-Density Polyethylene (LLDPE)

Linear low-density polyethylene (LLDPE) is a substantially linearpolymer (polyethylene), with significant numbers of short branches,commonly made by copolymerization of ethylene with longer-chain olefins.Linear low-density polyethylene differs structurally from conventionallow-density polyethylene because of the absence of long chain branching.The linearity of LLDPE results from the different manufacturingprocesses of LLDPE and LDPE. In general, LLDPE is produced at lowertemperatures and pressures by copolymerization of ethylene and suchhigher alpha olefins as butene, hexene, or octene. The copolymerizationprocess produces an LLDPE polymer that has a narrower molecular weightdistribution than conventional LDPE and in combination with the linearstructure, significantly different rheological properties.

The production of LLDPE is initiated by transition metal catalysts,particularly Ziegler or Philips type of catalyst. The actualpolymerization process can be done in either solution phase or gas phasereactors. Usually, octene is the copolymer in solution phase whilebutene and hexene are copolymerized with ethylene in a gas phasereactor. The LLDPE resin produced in a gas phase reactor is in granularform and may be sold as granules or processed into pellets. LLDPE hashigher tensile strength and higher impact and puncture resistance thanLDPE. It is very flexible and elongates under stress. It can be used tomake thinner films, with better environmental stress crackingresistance. It has good resistance to chemicals and to ultravioletradiation. It has good electrical properties. However it is not as easyto process as LDPE, has lower gloss, and narrower range for heatsealing.

LDPE and LLDPE have unique theoretical or melt flow properties. LLDPE isless shear sensitive because of its narrower molecular weightdistribution and shorter chain branching. During a shear process, suchas extrusion, LLDPE remains more viscous, therefore harder to processthan an LDPE of equivalent melt index. The lower shear sensitivity ofLLDPE allows for a faster stress relaxation of the polymer chains duringextrusion and therefore the physical properties are susceptible tochanges in blow-up ratios. In melt extension, LLDPE has lower viscosityat all strain rates. This means it will not strain harden the way LDPEdoes when elongated. As the deformation rate of the polyethyleneincreases, LDPE demonstrates a dramatic rise in viscosity because ofchain entanglement. This phenomena is not observed with LLDPE because ofthe lack of long-chain branching in LLDPE allows the chains to “slideby” one another upon elongation without becoming entangled. Thischaracteristic is important for film applications because LLDPE filmscan be downgauged easily while maintaining high strength and toughness.

Properties of film grade LLDPE include: Density 0.902-0.960 g/cc;Moisture Vapor Transmission 0.240-0.470 cc-mm/mg-24 hr-atm; Water VaporTransmission 6.00-8.00 g/m²/day; Oxygen Transmission 0.720-236cc-mm/mg-24 hr-atm; Oxygen Transmission Rate 3500-5000 cc/m²/day;Viscosity 37000-79000 cP @Temperature 190-190° C.; 37000-79000 cP @ShearRate 300-5000 l/s; 37000-79000 cP @Shear Rate 300-5000 1/s; Thickness12.7-76.2 microns; Melt Flow 0.200-40.0 g/10 min; Base Resin Melt Index0.700-3.50 g/10 min; Antiblock Level 3500-9000 ppm; Slip Level0.000-1700 ppm; Tensile Strength, Ultimate 9.80-26.2 MPa; Film TensileStrength at Yield, MD 7.38-74.0 MPa; Film Tensile Strength at Yield, TD6.90-77.0 MPa; Film Elongation at Break, MD 80.0-1460%; Film Elongationat Break, TD 460-1710%; Film Elongation at Yield, MD 435-640%; FilmElongation at Yield, TD 670-890%; Tensile Strength, Yield 9.70-22.1 MPa;Elongation at Break 8.00-1000%; Modulus of Elasticity 0.0110-0.413 GPa;Secant Modulus, MD 0.0103-0.717 GPa; Secant Modulus, TD 0.0106-0.869GPa; Impact 48.0-65.0; Impact Test 0.452-5.00 J; Coefficient of Friction0.100-2.00; Coefficient of Friction, Static 0.170-1.00; Elmendorf TearStrength MD 25.0-1080 g 2; Elmendorf Tear Strength TD 180-1470 g;Elmendorf Tear Strength, MD 0.0750-20.9 g/micron; Elmendorf TearStrength, TD 0.275-37.8 g/micron; Dart Drop 1.57-42.5 g/micron; DartDrop Test 30.0-1350 g; Seal Strength 1800-2400 g/25 mm; Film TensileStrength at Break, MD 9.65-82.7 MPa; Film Tensile Strength at Break, TD7.24-55.1 MPa; Heat Seal Strength Initiation Temperature 72.0-100° C.;Melting Point 120-128° C.; Crystallization Temperature 104-115° C.;Vicat Softening Point 93.0-123° C.; Haze 0.700-80.0%; Gloss 3.00-140%;Processing Temperature 90.0-310° C.; Die Opening 0.0810-0.254 cm;Blow-up Ratio (BUR) 1.50-4.00.

Ethylene Vinyl Alcohol (EVOH)

Ethylene Vinyl Alcohol is a formal copolymer of ethylene and vinylalcohol. Because the latter monomer mainly exists as its tautomeracetaldehyde, the copolymer is prepared by polymerization of ethyleneand vinyl acetate followed by hydrolysis. The plastic resin is commonlyused in food applications, and in plastic gasoline tanks forautomobiles. Its primary purpose is to provide barrier properties,primarily as an oxygen barrier for improved food packaging shelf lifeand as a hydrocarbon barrier for fuel tanks. EVOH is typicallycoextruded or laminated as a thin layer between cardboard, foil, orother plastics. EVOH copolymer is defined by the mole % ethylenecontent: lower ethylene content grades have higher barrier properties;higher ethylene content grades have lower temperatures for extrusion.

Ethylene Vinyl Alcohol (EVOH) is one of the most common clear highbarrier films used today. It is applied as a discrete layer in acoextrusion. EVOH provides excellent oxygen barrier properties(0.006-0.12 cc-mil/100 in²-day). The barrier that a particular EVOH filmprovides is dependent upon a number of factors: mole percent—as theethylene mole percent increases, the barrier decreases; degree ofcrystallinity—as the degree of crystallinity increases, the barrierproperties improve; thickness—as with all films, as the thicknessincreases, the barrier increases; temperature—as the temperatureincreases, the barrier decreases; humidity—at high humidity levels, thebarrier provided by EVOH drops rapidly (it is the humidity level at theEVOH interface rather than ambient humidity that is critical). Inaddition to providing an excellent oxygen barrier, EVOH is also anexcellent odor and aroma barrier. It has the added advantage of beingthermoformable making it popular for 3D applications.

EVALCA EVAL® EF-XL Ethylene Vinyl Alcohol Copolymer Film has thefollowing properties: Moisture Vapor Transmission 0.600 cc-mm/mg-24hr-atm 40° C., 90% RH; Oxygen Transmission 0.00400 cc-mm/mg-24 hr-atm20° C.; 65% RH (permeability increases significantly at higher moisturecontent); thickness 15.2 microns; Film Elongation at Break, MD 100%10%/min.; ASTM D638 Film Elongation at Break, TD 100% 10%/min.; ASTMD638 Secant Modulus, MD 3.50 GPa; Youngs Modulus, ASTM D638, 10%/min.;Secant Modulus, TD 3.50 GPa; Youngs Modulus, ASTM D638, 10%/min.;Elmendorf Tear Strength MD 260 g; ASTM D638 Elmendorf Tear Strength TD330 g; ASTM D638 Elmendorf Tear Strength, MD 17.0 g/micron; ASTM D638Elmendorf Tear Strength, TD 21.7 g/micron; ASTM D638 Film TensileStrength at Break, MD 205 MPa 10%/min.; ASTM D638 Film Tensile Strengthat Break, TD 195 MPa 10%/min.; Surface Resistance 2.70e+15 ohm;Dielectric Constant 5.00; Dissipation Factor 0.220; Specific HeatCapacity 2.40 J/g-° C.; Thermal Conductivity 0.340 W/m-K; Melting Point181° C. DSC; Haze 0.500% 65% RH; Gloss 95.0% 65% RH. EVAL® ethylenevinyl alcohol films are available from Kuraray America, Inc. of Houston,Tex.

Nylon

Nylon is a generic designation for a family of synthetic polymers knowngenerically as polyamides. Nylon is a thermoplastic silky material.There are two common methods of making nylon for fiber applications. Inone approach, molecules with an acid (COOH) group on each end arereacted with molecules containing amine (NH2) groups on each end. Theresulting nylon is named on the basis of the number of carbon atomsseparating the two acid groups and the two amines. These are formed intomonomers of intermediate molecular weight, which are then reacted toform long polymer chains.

Solid nylon is used for mechanical parts such as machine screws, gearsand other low- to medium-stress components previously cast in metal.Engineering-grade nylon is processed by extrusion, casting, andinjection molding. Solid nylon is used in hair combs. Type 6/6 Nylon 101is the most common commercial grade of nylon, and Nylon 6 is the mostcommon commercial grade of molded nylon. Nylon is available inglass-filled variants which increase structural and impact strength andrigidity, and molybdenum sulfide-filled variants which increaselubricity.

Aramids are another type of polyamide with quite different chainstructures which include aromatic groups in the main chain. Suchpolymers make excellent ballistic fibers.

Nylons are condensation copolymers formed by reacting equal parts of adiamine and a dicarboxylic acid, so that peptide bonds form at both endsof each monomer in a process analogous to polypeptide biopolymers. Thenumerical suffix specifies the numbers of carbons donated by themonomers; the diamine first and the diced second. The most commonvariant is nylon 6-6 which refers to the fact that the diamine(hexamethylene diamine) and the diacid (adipic acid) each donate 6carbons to the polymer chain. As with other regular copolymers likepolyesters and polyurethanes, the “repeating unit” consists of one ofeach monomer, so that they alternate in the chain. Since each monomer inthis copolymer has the same reactive group on both ends, the directionof the amide bond reverses between each monomer, unlike naturalpolyamide proteins which have overall directionality. In the laboratory,nylon 6-6 can also be made using adipoyl chloride instead of adipic. Itis difficult to get the proportions exactly correct, and deviations canlead to chain termination at molecular weights less than a desirable10,000 daltons. To overcome this problem, a crystalline, solid “nylonsalt” can be formed at room temperature, using an exact 1:1 ratio of theacid and the base to neutralize each other. Heated to 285° C., the saltreacts to form nylon polymer. Above 20,000 daltons, it is impossible tospin the chains into yarn, so to combat this some acetic acid is addedto react with a free amine end group during polymer elongation to limitthe molecular weight. In practice, and especially for nylon 6,6, themonomers are often combined in a water solution. The water used to makethe solution is evaporated under controlled conditions, and theincreasing concentration of “salt” is polymerized to the final molecularweight.

Homopolymer nylon 6, or polycaprolactam, is not a condensation polymer,but formed by a ring-opening polymerization (alternatively made bypolymerizing aminocaproic acid). The peptide bond within the caprolactamis broken with the exposed active groups on each side being incorporatedinto two new bonds as the monomer becomes part of the polymer backbone.In this case, all amide bonds lie in the same direction, but theproperties of nylon 6 are sometimes indistinguishable from those ofnylon 6,6-except for melt temperature (N₆ is lower) and some fiberproperties in products like carpets and textiles. There is also nylon 9.

Nylon 5,10, made from pentamethylene diamine and sebacic acid hassuperior properties, but is more expensive to make. In keeping with thisnaming convention, “nylon 6,12” (N-6,12) or “PA-6,12” is a copolymer ofa 6C diamine and a 12C diacid. Similarly for N-5,10 N-6,11; N-10,12,etc. Other nylons include copolymerized dicarboxylic acid/diamineproducts that are not based upon the monomers listed above. For example,some aromatic nylons are polymerized with the addition of diacids liketerephthalic acid (Kevlar) or isophthalic acid (Nomex), more commonlyassociated with polyesters. There are copolymers of N-6,6/N₆; copolymersof N-6,6/N-6/N-12; and others. Because of the way polyamides are formed,nylon can seem to be limited to unbranched, straight chains. But “star”branched nylon can be produced by the condensation of dicarboxylic acidswith polyamines having three or more amino groups.

Above their melting temperatures, Tm, thermoplastics like nylon areamorphous solids or viscous fluids in which the chains approximaterandom coils. Below Tm, amorphous regions alternate with regions whichare lamellar crystals. The amorphous regions contribute elasticity andthe crystalline regions contribute strength and rigidity. The planaramide (—CO—NH—) groups are very polar, so nylon forms multiple hydrogenbonds among adjacent strands. Because the nylon backbone is so regularand symmetrical, especially if all the amide bonds are in the transconfiguration, nylons often have high crystallinity and make excellentfibers. The amount of crystallinity depends on the details of formation,as well as on the kind of nylon. Apparently it can never be quenchedfrom a melt as a completely amorphous solid.

Nylon 6,6 can have multiple parallel strands aligned with theirneighboring peptide bonds at coordinated separations of exactly 6 and 4carbons for considerable lengths, so the carbonyl oxygens and amidehydrogens can line up to form interchain hydrogen bonds repeatedly,without interruption. Nylon 5,10 can have coordinated runs of 5 and 8carbons. Thus parallel (but not antiparallel) strands can participate inextended, unbroken, multi-chain ß-pleated sheets, a strong and toughsupermolecular structure similar to that found in natural silk fibroinand the ß-keratins in feathers (proteins have only an amino acida-carbon separating sequential —CO—NH— groups). Nylon 6 will formuninterrupted H-bonded sheets with mixed directionalities, but theß-sheet wrinkling is somewhat different. The three-dimensionaldisposition of each alkane hydrocarbon chain depends on rotations aboutthe 109.47° tetrahedral bonds of singly-bonded carbon atoms.

Block nylon tends to be less crystalline, except near the surfaces dueto shearing stresses during formation. Nylon is clear and colorless, ormilky, but is easily dyed. Multistranded nylon cord and rope is slipperyand tends to unravel. The ends can be melted and fused with a heatsource such as a flame or electrode to prevent this.

When dry, polyamide is a good electrical insulator. However, polyamideis hygroscopic. The absorption of water will change some of thematerial's properties such as its electrical resistance. Nylon is lessabsorbent than wool or cotton.

Nylon can be used as the matrix material in composite materials, withreinforcing fibers like glass or carbon fiber, and has a higher densitythan pure nylon. Such thermoplastic composites (25% glass fiber) arefrequently used in car components next to the engine, such as intakemanifolds, where the good heat resistance of such materials makes themfeasible competitors to metals.

All nylons are susceptible to hydrolysis, especially by strong acids, areaction essentially the reverse of the synthetic reaction shown above.The molecular weight of nylon products so attacked drops fast, andcracks form quickly at the affected zones. Lower members of the nylons(such as nylon 6) are affected more than higher members such as nylon12. This means that nylon parts cannot be used in contact with sulfuricacid for example, such as the electrolyte used in lead-acid batteries.When being molded, nylon must be dried to prevent hydrolysis in themolding machine barrel since water at high temperatures can also degradethe polymer.

Polyimide (PI)

Polyimide is a polymer of imide monomers. Thermosetting polyimides arecommercially available as uncured resins, stock shapes, thin sheets,laminates and machines parts. Thermoplastic polyimides are very oftencalled pseudothermoplastic. There are two general types of polyimides.One type, so-called linear polyimides, is made by combining imides intolong chains. Aromatic heterocyclic polyimides are the other usual kind.Examples of polyimide films include Apical, Kapton, UPILEX, VTEC PI,Norton TH and Kaptrex. Polyimide parts and shapes include VTEC PI,Meldin, Vespel and typical monomers include pyromellitic dianhydride and4,4′-oxydianiline.

Thermosetting polyimides are known for thermal stability, good chemicalresistance, excellent mechanical properties, and characteristicorange/yellow color. Polyimides compounded with graphite or glass fiberreinforcements have flexural strengths of up to 50,000 psi and flexuralmoduli of 3,000,000 psi. Thermoset polyimides exhibit very low creep andhigh tensile strength. These properties are maintained during continuoususe to temperatures of 232° C. and for short excursions, as high as 482°C. Molded polyimide parts and laminates have very good heat resistance.Normal operating temperatures for such parts and laminates range fromcryogenic to those exceeding 260° C. Polyimides are also inherentlyresistant to flame combustion and do not usually need to be mixed withflame retardants. Most carry a UL rating of VTM-0. Polyimide laminateshave a flexural strength half life at 249° C. of 400 hours.

Typical polyimide parts are not affected by commonly used solvents andoils including hydrocarbons, esters, ethers, alcohols and freons. Theyalso resist weak acids but are not recommended for use in environmentsthat contain alkalis or inorganic acids. Some polyimides, such as CP1and CORIN XLS, are solvent-soluble and exhibit high optical clarity. Thesolubility properties lend them towards spray and low temperature cureapplications.

The polyimide materials are lightweight, flexible, resistant to heat andchemicals. Therefore, they are used in the electronics industry forflexible cables, as an insulating film on magnet wire and for medicaltubing. For example, in a laptop computer, the cable that connects themain logic board to the display (which must flex every time the laptopis opened or closed) is often a polyimide base with copper conductors.The semiconductor industry uses polyimide as a high-temperatureadhesive; it is also used as a mechanical stress buffer. Some polyimidecan be used like a photoresist; both “positive” and “negative” types ofphotoresist-like polyimide exist in the market.

Thermoset film polyimide has the following properties: Density 1.40-1.67g/cc; Water Absorption 1.40-3.00%; Moisture Absorption at Equilibrium0.400-1.80%; Water Absorption at Saturation 1.20-2.50%; Moisture VaporTransmission 2.40-17.5 cc-mm/mg-24 hr-atm; Oxygen Transmission 9.90cc-mm/mg-24 hr-atm; Thickness 22.0-187 microns; Film Tensile Strength atYield, MD 49.0-255 MPa; Film Tensile Strength at Yield, TD 100-160 MPa;Film Elongation at Break, MD 10.0-85.0%; Film Elongation at Yield, MD40.0-50.0%; Film Elongation at Yield, TD 45.0-55.0%; Tensile Strength,Yield 73.3-160 MPa; Elongation at Yield 10.0-45.0%; Poissons Ratio0.340; Secant Modulus 2.28-5.20 GPa; Secant Modulus, MD 1.76-9.12 GPa;Impact Test 0.686-1.56 J; Coefficient of Friction 0.400-0.480;Coefficient of Friction, Static 0.630; Tear Strength Test 7.20-430; PeelStrength 0.240 kN/m; Elmendorf Tear Strength MD 8.20-270 g; Film TensileStrength at Break, MD 98.1-736 MPa; Electrical Resistivity1.00e+10-2.30e+17 ohm-cm; 1.00e+15-1.00e+16 ohm-cm @Temperature 200° C.;Surface Resistance 10000-1.00e+17 ohm; 1.00e+15-1.00e+15 ohm@Temperature 200° C.; Dielectric Constant 2.70-4.00; Dielectric Strength48.0-272 kV/mm @Temperature 200° C.; Dissipation Factor 0.00130-0.0100;CTE, linear 12.0-20.0 μm/m-° C.; 32.0-40.0 μm/m-° C. @Temperature100-300° C.; Specific Heat Capacity 1.09-1.13 J/g-° C.; ThermalConductivity 0.120-0.289 W/m-K; Maximum Service Temperature, Air180-400° C.; Minimum Service Temperature, Air −269° C.; GlassTemperature 360-500° C.; Oxygen Index 37.0-66.0%; Shrinkage0.0100-0.200%; Refractive Index 1.70.

Liquid Crystal Polymer (LCP)

Liquid-crystal polymers (LCPs) are a class of aromatic polyesterpolymers. They are extremely unreactive and inert, and highly resistantto fire. Liquid crystallinity in polymers may occur either by dissolvinga polymer in a solvent (lyotropic liquid-crystal polymers) or by heatinga polymer above its glass or melting transition point (thermotropicliquid-crystal polymers). Liquid-crystal polymers are present inmelted/liquid or solid form. In liquid form liquid-crystal polymers haveprimarily applications in liquid-crystal displays (LCDs). In solid formthe main example of lyotropic LCPs is the commercial aramid known asKevlar. The chemical structure of this aramid consists of linearlysubstituted aromatic rings linked by amide groups. In a similar way,several series of thermotropic LCPs have been commercially produced byseveral companies (e.g., Vectra). A high number of LCPs, produced in the1980s, displayed order in the melt phase analogous to that exhibited bynonpolymeric liquid crystals. Processing of LCPs from liquid-crystalphases (or mesophases) gives rise to fibers and injected materialshaving high mechanical properties as a consequence of theself-reinforcing properties derived from the macromolecular orientationin the mesophase. Today, LCPs can be melt-processed on conventionalequipment at high speeds with excellent replication of mold details.

A unique class of partially crystalline aromatic polyesters based onp-hydroxybenzoic acid and related monomers, liquid-crystal polymers iscapable of forming regions of highly ordered structure while in theliquid phase. However, the degree of order is somewhat less than that ofa regular solid crystal. Typically LCPs have a high mechanical strengthat high temperatures, extreme chemical resistance, inherent flameretardancy, and good weatherability. Liquid-crystal polymers come in avariety of forms from sinterable high temperature to injection moldablecompounds. LCP can be welded, though the lines created by welding are aweak point in the resulting product. LCP has a high Z-axis coefficientof thermal expansion.

LCPs are exceptionally inert. They resist stress cracking in thepresence of most chemicals at elevated temperatures, including aromaticor halogenated hydrocarbons, strong acids, bases, ketones, and otheraggressive industrial substances. Hydrolytic stability in boiling wateris excellent. Environments that deteriorate the polymers arehigh-temperature steam, concentrated sulfuric acid, and boiling causticmaterials. Because of their various properties, LCPs are useful forelectrical and mechanical parts, food containers, and any otherapplications requiring chemical inertness and high strength.

High-Density Polyethylene (HDPE)

High-density polyethylene (HDPE) or polyethylene high-density (PEHD) isa polyethylene thermoplastic made from petroleum. HDPE has littlebranching, giving it stronger intermolecular forces and tensile strengththan lower-density polyethylene. It is also harder and more opaque andcan withstand somewhat higher temperatures (120° C. for short periods,110° C. continuously). High-density polyethylene, unlike polypropylene,cannot withstand normally-required autoclaving conditions. The lack ofbranching is ensured by an appropriate choice of catalyst (e.g.,Ziegler-Natta catalysts) and reaction conditions. HDPE contains thechemical elements carbon and hydrogen. Hollow goods manufactured throughblow molding are the most common application area for HDPE.

Polypropylene (PP)

Polypropylene or polypropene (PP) is a thermoplastic polymer, made bythe chemical industry and used in a wide variety of applications,including packaging, textiles (e.g. ropes, thermal underwear andcarpets), stationery, plastic parts and reusable containers of varioustypes, laboratory equipment, loudspeakers, automotive components, andpolymer banknotes. An addition polymer made from the monomer propylene,it is rugged and unusually resistant to many chemical solvents, basesand acids.

Most commercial polypropylene is isotactic and has an intermediate levelof crystallinity between that of low density polyethylene (LDPE) andhigh density polyethylene (HDPE); its Young's modulus is alsointermediate. PP is normally tough and flexible, especially whencopolymerized with ethylene. This allows polypropylene to be used as anengineering plastic, competing with materials such as ABS. Polypropyleneis reasonably economical, and can be made translucent when uncolored butis not as readily made transparent as polystyrene, acrylic or certainother plastics. It is often opaque and/or colored using pigments.Polypropylene has good resistance to fatigue.

Polypropylene has a melting point of −160° C. (320° F.), as determinedby Differential scanning calorimetry (DSC). The MFR (Melt Flow Rate) orMFI (Melt Flow Index) is a measure of PP's molecular weight. This helpsto determine how easily the molten raw material will flow duringprocessing. Higher MFR PPs fill the plastic mold more easily during theinjection or blow molding production process. As the melt flowincreases, however, some physical properties, like impact strength, willdecrease.

There are three general types of PP: homopolymer, random copolymer andblock copolymer. The comonomer used is typically ethylene.Ethylene-propylene rubber or EPDM added to PP homopolymer increases itslow temperature impact strength. Randomly polymerized ethylene monomeradded to PP homopolymer decreases the polymer crystallinity and makesthe polymer more transparent.

Polypropylene is liable to chain degradation from exposure to UVradiation such as that present in sunlight. For external applications,UV-absorbing additives must be used. Carbon black also provides someprotection from UV attack. The polymer can also be oxidized at hightemperatures, a common problem during molding operations. Anti-oxidantsare normally added to prevent polymer degradation.

The relative orientation of each methyl group relative to the methylgroups on neighboring monomers has a strong effect on the finishedpolymer's ability to form crystals, because each methyl group takes upspace and constrains backbone bending.

Like most other vinyl polymers, useful polypropylene cannot be made byradical polymerization due to the higher reactivity of the allylichydrogen (leading to dimerization) during polymerization. Moreover, thematerial that can result from such a process can have methyl groupsarranged randomly, so called atactic PP. The lack of long-range orderprevents any crystallinity in such a material, giving an amorphousmaterial with very little strength and only specialized qualitiessuitable for niche end uses.

A Ziegler-Natta catalyst is able to limit incoming monomers to aspecific orientation, only adding them to the polymer chain if they facethe right direction. Most commercially available polypropylene is madewith such Ziegler-Natta catalysts, which produce mostly isotacticpolypropylene. With the methyl group consistently on one side, suchmolecules tend to coil into a helical shape; these helices then line upnext to one another to form the crystals that give commercialpolypropylene many of its desirable properties.

More precisely engineered Kaminsky catalysts have been made, which offera much greater level of control. Based on metallocene molecules, thesecatalysts use organic groups to control the monomers being added, sothat a proper choice of catalyst can produce isotactic, syndiotactic, oratactic polypropylene, or even a combination of these. Aside from thisqualitative control, they allow better quantitative control, with a muchgreater ratio of the desired tacticity than previous Ziegler-Nattatechniques. They also produce narrower molecular weight distributionsthan traditional Ziegler-Natta catalysts, which can further improveproperties.

To produce a rubbery polypropylene, a catalyst can be made which yieldsisotactic polypropylene, but with the organic groups that influencetacticity held in place by a relatively weak bond. After the catalysthas produced a short length of polymer which is capable ofcrystallization, light of the proper frequency is used to break thisweak bond, and remove the selectivity of the catalyst so that theremaining length of the chain is atactic. The result is a mostlyamorphous material with small crystals embedded in it. Since each chainhas one end in a crystal but most of its length in the soft, amorphousbulk, the crystalline regions serve the same purpose as vulcanization.

Melt processing of polypropylene can be achieved via extrusion andmolding. Common extrusion methods include production of melt blown andspun bond fibers to form long rolls for future conversion into a widerange of useful products such as face masks, filters, nappies and wipes.The most common shaping technique is injection molding, which is usedfor parts such as cups, cutlery, vials, caps, containers, housewares andautomotive parts such as batteries. The related techniques of blowmolding and injection-stretch blow molding are also used, which involveboth extrusion and molding.

The large number of end use applications for PP is often possiblebecause of the ability to tailor grades with specific molecularproperties and additives during its manufacture. For example, antistaticadditives can be added to help PP surfaces resist dust and dirt. Manyphysical finishing techniques can also be used on PP, such as machining.Surface treatments can be applied to PP parts in order to promoteadhesion of printing ink and paints.

Since polypropylene is resistant to fatigue, most plastic living hinges,such as those on flip-top bottles, are made from this material. However,it is important to ensure that chain molecules are oriented across thehinge to maximize strength. Very thin sheets of polypropylene are usedas a dielectric within certain high performance pulse and low loss RFcapacitors.

High-purity piping systems are built using polypropylene. Stronger, morerigid piping systems, intended for use in potable plumbing, hydronicheating and cooling, and reclaimed water applications, are alsomanufactured using polypropylene. This material is often chosen for itsresistance to corrosion and chemical leaching, its resilience againstmost forms of physical damage, including impact and freezing, and itsability to be joined by heat fusion rather than gluing.

Many plastic items for medical or laboratory use can be made frompolypropylene because it can withstand the heat in an autoclave. Itsheat resistance also enables it to be used as the manufacturing materialof consumer-grade kettles. Food containers made from it will not melt inthe dishwasher, and do not melt during industrial hot filling processes.For this reason, most plastic tubs for dairy products are polypropylenesealed with aluminum foil (both heat-resistant materials). After theproduct has cooled, the tubs are often given lids made of a lessheat-resistant material, such as LDPE or polystyrene. Such containersprovide a good hands-on example of the difference in modulus, since therubbery (softer, more flexible) feeling of LDPE with respect to PP ofthe same thickness is readily apparent. Rugged, translucent, reusableplastic containers made in a wide variety of shapes and sizes forconsumers from various companies such as Rubbermaid and Sterilite arecommonly made of polypropylene, although the lids are often made ofsomewhat more flexible LDPE so they can snap on to the container toclose it. Polypropylene can also be made into disposable bottles tocontain liquid, powdered or similar consumer products, although HDPE andpolyethylene terephthalate are commonly also used to make bottles.Plastic pails, car batteries, wastebaskets, cooler containers, dishesand pitchers are often made of polypropylene or HDPE, both of whichcommonly have rather similar appearance, feel, and properties at ambienttemperature.

Polypropylene is a major polymer used in nonwovens, with over 50% usedfor diapers or sanitary products where it is treated to absorb water(hydrophilic) rather than naturally repelling water (hydrophobic). Otherinteresting non woven uses include filters for air, gas and liquidswhere the fibers can be formed into sheets or webs that can be pleatedto form cartridges or layers that filter in various efficiencies in the0.5 to 30 micron range. Such applications can be seen in the house aswater filters or air conditioning type filters. The high surface areaand naturally hydrophobic polypropylene nonwovens are ideal absorbers ofoil spills with the familiar floating barriers near oil spills onrivers.

A common application for polypropylene is as Biaxially Orientedpolypropylene (BOPP). These BOPP sheets are used to make a wide varietyof materials including clear bags. When polypropylene is biaxiallyoriented, it becomes crystal clear and serves as an excellent packagingmaterial for artistic and retail products.

Polypropylene's most common medical use is in the synthetic,nonabsorbable suture Prolene, manufactured by Ethicon Inc.

Polypropylene is most commonly used for plastic moldings where it isinjected into a mold while molten, forming complex shapes at relativelylow cost and high volume, examples include bottle tops, bottles andfittings.

Recently it has been produced in sheet form and this has been widelyused for the production of stationary folders, packaging and storageboxes. The wide color range, durability and resistance to dirt make itideal as a protective cover for papers and other materials. It is usedin Rubik's cube stickers because of these characteristics.

Expanded Polypropylene (EPP) is a foam form of polypropylene. EPP hasvery good impact characteristics due to its low stiffness; this allowsEPP to resume its shape after impacts. EPP is extensively used in modelaircraft and other radio controlled vehicles by hobbyists. This ismainly due to its ability to absorb impacts, making this an idealmaterial for RC aircraft for beginners and amateurs.

Silicon Dioxide (SiO₂)

The chemical compound silicon dioxide, also known as silica, is an oxideof silicon with a chemical formula of SiO₂. Oxides of silicon, commonlyreferred to as “SiOx,” include silicon dioxide. Silica is most commonlyfound in nature as sand or quartz, as well as in the cell walls ofdiatoms. It is a principal component of most types of glass andsubstances such as concrete. Silica is the most abundant mineral in theEarth's crust. SiO₂ has a number of distinct crystalline forms inaddition to amorphous forms. With the exception of stishovite andfibrous silica, all of the crystalline forms involve tetrahedral SiO₄units linked together by shared vertices in different arrangements.Silicon-oxygen bond lengths vary between the different crystal forms. Ina-quartz the Si—O—Si angle is 144°. The only stable form under normalconditions is a-quartz and this is the form in which crystalline silicondioxide is usually encountered.

Silicon dioxide is formed when silicon is exposed to oxygen (or air). Avery thin layer (approximately 1 nm or 10 Å) of so-called ‘native oxide’is formed on the surface when silicon is exposed to air under ambientconditions. Higher temperatures and alternative environments are used togrow well-controlled layers of silicon dioxide on silicon, for exampleat temperatures between 600 and 1200° C., using the so-called “dry” or“wet” oxidation with O₂ or H₂O, respectively. The thickness of the layerof silicon replaced by the dioxide is 44% of the thickness of thesilicon dioxide layer produced. Alternative methods used to deposit alayer of SiO₂ include: Low temperature oxidation (400-450° C.) ofsilane; Decomposition of tetraethyl orthosilicate (TEOS) at 680-730° C.;Plasma enhanced chemical vapor deposition using TEOS at about 400° C.;Polymerization of tetraethyl orthosilicate (TEOS) at below 100° C. usingamino acid as catalyst.

Pyrogenic silica (sometimes called fumed silica or silica fume), whichis a very fine particulate form of silicon dioxide, is prepared byburning SiCl4 in an oxygen rich hydrocarbon flame to produce a “smoke”of SiO₂. Amorphous silica, silica gel, is produced by the acidificationof solutions of sodium silicate to produce a gelatinous precipitate thatis then washed and then dehydrated to produce colorless microporoussilica.

Aluminum Oxide (Al₂O₃)

Aluminum oxide is an amphoteric oxide of aluminum with the chemicalformula Al₂O₃. It is also commonly referred to as alumina, corundum,sapphire, ruby or aloxite. Aluminum oxide is an electrical insulator buthas a relatively high thermal conductivity (40 Wm⁻¹K⁻¹) for a ceramicmaterial. In its most commonly occurring crystalline form, calledcorundum or a-aluminum oxide, its hardness makes it suitable for use asan abrasive and as a component in cutting tools. Aluminum oxide isresponsible for resistance of metallic aluminum to weathering. Metallicaluminum is very reactive with atmospheric oxygen, and a thinpassivation layer of alumina (4 nm thickness) forms in about 100picoseconds on any exposed aluminum surface. This layer protects themetal from further oxidation. The thickness and properties of this oxidelayer can be enhanced using a process called anodizing. A number ofalloys, such as aluminum bronzes, exploit this property by including aproportion of aluminum in the alloy to enhance corrosion resistance. Thealumina generated by anodizing is typically amorphous, but dischargeassisted oxidation processes such as plasma electrolytic oxidationresult in a significant proportion of crystalline alumina in thecoating, enhancing its hardness. The most common form of crystallinealumina, a-aluminum oxide, is known as corundum. Alumina also exists inother phases. Each has a unique crystal structure and properties.Aluminum hydroxide minerals are the main component of bauxite, theprincipal ore of aluminum. Alumina tends to be multi-phase; e.g.,constituting several of the alumina phases rather than solely corundum.

Polyvinyl Alcohol (PVOH, PVA, or PVAL)

Polyvinyl alcohol (PVOH, PVA, or PVAL) is a water-soluble syntheticpolymer. Polyvinyl alcohol has excellent film forming, emulsifying, andadhesive properties. It is also resistant to oil, grease and solvent. Itis odorless and nontoxic. It has high tensile strength and flexibility,as well as high oxygen and aroma barrier properties. However theseproperties are dependent on humidity, in other words, with higherhumidity more water is absorbed. The water, which acts as a plasticizer,will then reduce its tensile strength, but increase its elongation andtear strength. PVA is fully degradable and is a quick dissolver. PVA hasa melting point of 230° C. and 180-190° C. for the fully hydrolyzed andpartially hydrolyzed grades, respectively. It decomposes rapidly above200° C. as it can undergo pyrolysis at high temperatures.

PVA is an atactic material but exhibits crystallinity as the hydroxylgroups are small enough to fit into the lattice without disrupting it.Unlike most vinyl polymers, PVA is not prepared by polymerization of thecorresponding monomer. The monomer, vinyl alcohol, almost exclusivelyexists as the tautomeric form, acetaldehyde. PVA instead is prepared bypartial or complete hydrolysis of polyvinyl acetate to remove acetategroups.

Nanopolymers

Polymer nanocomposite (PNC) is a polymer or copolymer having dispersedin its nanoparticles. These may be of different shape (e.g., platelets,fibers, spheroids), but at least one dimension is in the range of 1 to50 nm. The transition from micro- to nano-particles leads to changes inphysical as well as chemical properties. Two of the major factors inthis are the increase in the ratio of the surface area to volume, andthe size of the particle. The increase in surface area-to-volume ratio,which increases as the particles get smaller, leads to an increasingdominance of the behavior of atoms on the surface area of particle overthat of those interior of the particle. This affects the properties ofthe particles when they are reacting with other particles. Because ofthe higher surface area of the nano-particles the interaction with theother particles within the mixture is more and this increases thestrength, heat resistance etc and many factors do change for themixture.

An example of a nanopolymer is silicon nanospheres which show quitedifferent characteristics. The particle size is 40-100 nm and it is muchharder than silicon (a hardness between that of sapphire and diamond).Many technical applications of biological objects like proteins, virusesor bacteria such as chromatography, optical information technology,sensors, catalysis and drug delivery require their immobilization.Carbon nanotubes, gold particles and synthetic polymers are used forthis purpose. This immobilization has been achieved predominantly byadsorption or by chemical binding and to a lesser extent byincorporating these objects as guests in host matrices. In the guesthost systems, an ideal method for the immobilization of biologicalobjects and their integration into hierarchical architectures should bestructured on a nanoscale to facilitate the interactions of biologicalnano-objects with their environment. Due to the large number of naturalor synthetic polymers available and the advanced techniques developed toprocess such systems to nanofibers, rods, tubes etc make polymers a goodplatform for the immobilization of biological objects.

Polymer fibers are, in general, produced on a technical scale byextrusion, e.g., a polymer melt or a polymer solution is pumped throughcylindrical dies and spun/drawn by a take-up device. The resultingfibers have diameters typically on the 10-μm scale or above. To comedown in diameter into the range of several hundreds of nanometers oreven down to a few nanometers, electrospinning is today still theleading polymer processing technique available. A strong electric fieldof the order of 103 V/cm is applied to the polymer solution dropletsemerging from a cylindrical die. The electric charges, which areaccumulated on the surface of the droplet, cause droplet deformationalong the field direction, even though the surface tension counteractsdroplet evolution. In supercritical electric fields, the field strengthoverbears the surface tension and a fluid jet emanates from the droplettip. The jet is accelerated towards the counter electrode. During thistransport phase, the jet is subjected to strong electrically drivencircular bending motions that cause a strong elongation and thinning ofthe jet, a solvent evaporation until, finally, the solid nanofiber isdeposited on the counter electrode.

Electro spinning, co-electrospinning, and the template methods based onnanofibers yield nano-objects which are, in principle, infinitivelylong. For a broad range of applications including catalysis, tissueengineering, and surface modification of implants this infinite lengthis an advantage. But in some applications like inhalation therapy orsystemic drug delivery, a well-defined length is required. The templatemethod to be described in the following has the advantage such that itallows the preparation of nanotubes and nanorods with very highprecision. The method is based on the use of well defined poroustemplates, such as porous aluminum or silicon. The basic concept of thismethod is to exploit wetting processes. A polymer melt or solution isbrought into contact with the pores located in materials characterizedby high energy surfaces such as aluminum or silicon. Wetting sets in andcovers the walls of the pores with a thin film with a thickness of theorder of a few tens of nanometers. This process happens typically withina minute for temperatures about 50 K above the melting temperature orglass transition temperature, even for highly viscous polymers, such as,for instance, polytetrafluoroethylene, and this holds even for poreswith an aspect ratio as large as 10,000. To obtain nanotubes, thepolymer/template system is cooled down to room temperature or thesolvent is evaporated, yielding pores covered with solid layers. Theresulting tubes can be removed by mechanical forces for tubes up to 10μm in length, e.g., by just drawing them out from the pores or byselectively dissolving the template. The diameter of the nanotubes, thedistribution of the diameter, the homogeneity along the tubes, and thelengths can be controlled.

The size-dependent and pressure-dependent glass transition temperaturesof free-standing films or supported films having weak interactions withsubstrates decreases with decreasing of pressure and size. However, theglass transition temperature of supported films having stronginteraction with substrates increases of pressure and the decrease ofsize.

Nanocomposites are polymer structures that contain fillers, typicallysilicate nanoclays, with at least one dimension in the nanometer range.The fillers separate into tiny platelets that disperse into a matrix oflayers. Because the matrix of layers creates a tortuous path for gassestrying to permeate through the film, the barrier properties of themodified polymer are improved. However, the challenge is to ensure thatthat the filler dispersion is consistent. In addition to better barrierproperties, nanocomposites modified films also have improved dimensionalstability and stiffness and, because crystallinity is increased,enhanced clarity. Nanocomposite masterbatches are commercially availablefor nylon and polyolefins. The oxygen barrier of nylon nanocompositefilms can be as much as 50 percent higher than a nonmodified nylon.Polyethylene and polypropylene nanocomposite structures have shownimprovement in gas barrier of 25 to 50 percent and in water vapor of 10to 15 percent in laboratory settings. Achieving consistent barrierproperties on a commercial scale remains challenging. Nanocompositetechnology is very much an emerging science. It shows a great deal ofpromise and as more options become available for film applications itwill have a significant impact on barrier material options.

Saran

Saran is the trade name for a number of polymers made from vinylidenechloride (especially polyvinylidene chloride or PVDC), along with othermonomers. Saran film has a very low permeability to water vapor, flavorand aroma molecules, and oxygen compared to other plastics. The barrierto oxygen prevents food spoilage, and the barrier to flavor and aromamolecules helps food retain its flavor and aroma. Saran also possessesgas barrier properties.

Polytrimethylene Terephthalate (PTT)

Polytrimethylene Terephthalate (PTT) is a semi crystalline polymer thathas many of the same advantages as PET. PTT exhibits good tensilestrength, flexural strength, and stiffness. It has excellent flow andsurface finish. PTT can have more uniform shrinkage and betterdimensional stability in some applications than competingsemicrystalline materials. PTT has excellent resistance to a broad rangeof chemicals at room temperature, including aliphatic hydrocarbons,gasoline, carbon tetrachloride, perchloroethylene, oils, fats, alcohols,glycols, esters, ethers and dilute acids and bases. Strong bases mayattack PTT compounds. Impact modifiers and reinforcing fibers (longglass, short glass, or carbon) can be used to increase the impactproperties, as well as the strength and stiffness of PTT.

Polytrimethylene naphthalate (PTN)

Poly(trimethylene phthalates or naphthalate) and copolymers are aromaticpolyesters made by polycondensation of 1,3-propanediol (PDO) andterephthalic acid (PTT), isophthalic acid (PTI) or naphthalic acid (PTN)and/or with comonomers (isophthalic acid, 1,4-butanediol, etc.). Filmsof PTN possess good barrier properties.

Polyethylene naphthalate (PEN)

Polyethylene naphthalate (PEN) is a polyester with good barrierproperties (even better than polyethylene terephthalate). Because itprovides a very good oxygen barrier, it is particularly well-suited forbottling beverages that are susceptible to oxidation, such as beer. Itis prepared from ethylene glycol and one or more naphthalenedicarboxylic acids by condensation polymerization.

Polyurethane

A polyurethane is any polymer consisting of a chain of organic unitsjoined by urethane (carbamate) links. Polyurethane polymers are formedthrough step-growth polymerization by reacting a monomer containing atleast two isocyanate functional groups with another monomer containingat least two hydroxyl (alcohol) groups in the presence of a catalyst.Polyurethane formulations cover an extremely wide range of stiffness,hardness, and densities. Though the properties of the polyurethane aredetermined mainly by the choice of polyol, the diisocyanate exerts someinfluence, and must be suited to the application. The cure rate isinfluenced by the functional group reactivity and the number offunctional isocyanate groups. The mechanical properties are influencedby the functionality and the molecular shape. The choice of diisocyanatealso affects the stability of the polyurethane upon exposure to light.Polyurethanes made with aromatic diisocyanates yellow with exposure tolight, whereas those made with aliphatic diisocyanates are stable.Softer, elastic, and more flexible polyurethanes result when lineardifunctional polyethylene glycol segments, commonly called polyetherpolyols, are used to create the urethane links. This strategy is used tomake spandex elastomeric fibers and soft rubber parts, as well as foamrubber. More rigid products result if polyfunctional polyols are used,as these create a three-dimensional cross-linked structure which, again,can be in the form of a low-density foam.

Polyether Block Amide (PEBAX®)

Polyether block amide is a thermoplastic elastomer or a flexiblepolyamide without plasticizer consisting of a regular linear chain ofrigid polyamide segments and flexible polyether segments.

Parylene C

Parylene is the trade name for a variety of chemical vapor depositedpoly(p-xylylene) polymers used as moisture barriers and electricalinsulators. Among them, Parylene C is the most popular due to itscombination of barrier properties, cost, and other manufacturingadvantages.

Silicone

Silicones, also referred to as polymerized siloxanes or polysiloxanes,are mixed inorganic-organic polymers with the chemical formula[R₂SiO]_(n), where R is an organic group such as methyl, ethyl, orphenyl. These materials consist of an inorganic silicon-oxygen backbone( . . . —Si—O—Si—O—Si—O— . . . ) with organic side groups attached tothe silicon atoms, which are four-coordinate. In some cases organic sidegroups can be used to link two or more of these —Si—O— backbonestogether. By varying the —Si—O— chain lengths, side groups, andcrosslinking, silicones can be synthesized with a wide variety ofproperties and compositions. They can vary in consistency from liquid togel to rubber to hard plastic. The most common siloxane is linearpolydimethylsiloxane (PDMS), a silicone oil. The second largest group ofsilicone materials is based on silicone resins, which are formed bybranched and cage-like oligosiloxanes.

Fabrication of the Composite Wall

The various layers of the composite wall, including the gas barrierlayers, need not be situated in any particular order, but those ofsuperior resistance to acidity, temperature, mechanical abrasion, andsuperior biocompatibility profile are preferably employed as layerscontacting the gastric environment. Those with superior resistance to,e.g., acidity and temperature, are preferably employed as layerscontacting the central lumen of the balloon.

The various layers of the wall can include a single layer or up to 10 ormore different monolayers; however, a film thickness of from 0.001inches (0.0254 cm) to 0.004 inches (0.010 cm) thick is desirable suchthat the resulting balloon compacted to fit into a swallowable capsule.The resulting composite wall preferably has good performancespecifications with respect to each category listed in Tables 1a-b.

Films that are co-extruded are advantageously employed, as someadhesives may contain leachables that are undesirable from abiocompatibility perspective. In addition, coextrusion allows for betterblending such that the materials maintain their original properties whencombined in this fashion and are less likely to be subject todelamination when exposed to gastric motility forces.

Combining films with similar properties, e.g., two film layers withexcellent gas barrier properties, in a composite wall is advantageousfor use in a gastric balloon containing nitrogen, oxygen, CO₂ or amixture thereof as the inflation gas or where the external environmentthe product is to be placed in, contains a mixture of gases includingCO₂, e.g., the stomach. A primary advantage of such composite films isthat restrictions on film thickness can be observed without sacrifice ofgas barrier properties. Such a configuration also contributes toreducing the effects of processing damage (e.g., manufacturing andcompacting) and damage due to exposure to in vivo conditions (e.g.,gastric motility forces).

In a particularly preferred embodiment, the composite wall includes aplurality of layers. The first layer is an outer protective layer thatis configured for exposure to the gastric environment. This layer isresistant to mechanical forces, exposure to water (vapor), abrasion, andhigh acidity levels. Nylon or more specifically, Nylon 12 isparticularly preferred for the layer exposed to the gastric environment,and is especially resistant to mechanical forces.

In an alternative embodiment, polyurethane is RF welded to saran toyield a 6-7 mil thick composite wall. In another embodiment, a fivelayer system is provided comprising a layer of saran sandwiched betweentwo polyurethane layers. Between the saran layer and each of thepolyurethane layers is a tie layer. The layers can be welded together,co-extruded or adhered using an adhesive. This tri-layer is thenco-extruded to Nylon on each side, and then a final sealing layer(polyethylene or the like) is added to one of the nylon layers for thetotal composite wall. A representative example of material combinationsthat are commercially available or manufacturable is provided in Table2. The orientation of the layers (innermost—in contact with the centralballoon lumen, or outermost—in contact with the gastric environment) isalso indicated if more than two layers are described to support asuggested composite wall.

Most of the film resins listed in Table 2 provide some degree of gasbarrier properties. Therefore, many can be used solely to form theballoon wall as a monolayer film; however they can also be used inconjunction with other film resins to meet the desired gas retention andmechanical specifications for the useful life of the balloon based onthe inflation gas and external environment the balloon is to be placedin. These film resins can also be coated with gas barrier coatingslisted in Tables 1a-b. Additional film layers can be added to form thetotal composite wall. While such additional layers may not impartsubstantial barrier properties, they can provide structural and/ormechanical properties, protection for the other layers of the compositewall that are susceptible to water vapor, humidity, pH, or the like, orother desirable properties. The film layers can be assembled usingvarious adhesives, via co-extrusion, via lamination, and/or using tielayers and such to create a composite wall that meets the requirementsof an intragastric balloon suitable for use for at least 25 days, or upto 90 days or more, with the specified gas retention properties. Table 2provides a list of layers and layer combinations suitable for use incomposite walls for an intragastric balloon. The composite description,resin abbreviation, configuration (single layer, bilayer, trilayer, orthe like) and trade name of commercially available combinations arelisted. The number of layers indicated does not include any adhesivelayers or tie layers used to fabricate the composite wall, such that a6-layer composite wall may, for example, have two or three adhesivelayers and/or tie layers that make up the total composite wall, andtherefore the total number of layers can be eight or nine in final form.The term “layer” as used herein is a broad term, and is to be given itsordinary and customary meaning to a person of ordinary skill in the art(and is not to be limited to a special or customized meaning), andrefers without limitation to a single thickness of a homogenoussubstance (e.g., a coating such as SiOx, or a layer such as PET), aswell as to a supporting layer having a coating thereon (wherein a“coating” is, e.g., a material typically employed in conjunction withsubstrate that provides structural support to the coating layer). Forexample, a PET-SiOx “layer” is referred to herein, wherein a layer ofSi-Ox is provided on a supporting PET layer.

TABLE 2 Example Film Composite Walls* Abbreviation Trade namepolyethylene terephthalate PET Mylar metalized oriented polyethylenemetalized OPET Custom terephthalate polyvinyl alcohol coated orientedPVOH coated OPP Bicor polypropylene metalized biaxially oriented nylon 6metalized OPA6 Custom Biaxally oriented Nylon/ethylene OPA/EVOH/OPAHoneywell vinyl alcohol/biaxally oriented Oxyshield Plus NylonNylon/ethylene vinyl alcohol/Low Nylon/EVOH/LDPE Custom DensityPolyethylene polyvinylidene chloride coated PVDC/OPET Mylar orientedpolyethylene terephthalate polyvinylidene chloride coated PVCD/OPPCustom oriented polypropylene polyvinylidene chloride coated PVCD/OPA6Honeywell biaxally oriented Nylon 6 Oxyshield high densitypolyethylene/ethylene HDPE/EVOH Custom vinyl alcoholpolypropylene/ethylene vinyl PP/EVOH Custom alcohol laminatepolyethylene PET/EVOH Custom terephthalate/ethylene vinyl alcoholmetalized oriented polypropylene metalized OPP Custom sealable PVDCcoated oriented PVDC coated PP Custom polypropylene polyvinylidenefluoride PVDF Custom Polyvinyl chloride PVC Custom polyvinyl fluoridePVF Tedlar polychlorofluoroethylene PCTFE ACLAR UltRx, SupRx, Rxamine-based epoxy coated Nylon epoxy coated PA6 Bairocade polyvinylchloride-polyvinylidene PVC-PVDC Custom chloride copolymer mediumdensity polyethylene MDPE Custom Nylon/Polypropylene Nylon/PP laminateCustom Nylon-High Density Polyethylene Nylon-HDPE laminate Custom Nylon12/Ethyl Methyl Co-extruded Nylon 12- Custom Co- Acrylate/PolyvinylideneChloride/ encapsulated PVDC-Nylon 12- extruded blend Ethyl MethylAcrylate/Nylon LLDPE + LDPE 12/Linear Low Density Polyethylene + LowDensity Polyethylene Multi-layer Nylon 12/Linear Low Co-extrudedmulti-layer Nylon 12- Custom Co- Density Polyethylene + Low LLDPE + LDPEExtruded Blend Density Polyethylene acetylene plasma coating on PET/ACustom polyester difluoroethylene coating on PET/DA Custom polyethyleneterephthalate oriented polypropylene OPP Custom cast propylene CPPCustom high density polyethylene HDPE Custom cyclic olefin copolymer COCCustom oriented polystyrene OPS Custom Fluorinated Ethylene PropyleneFEP Custom difluoroethylene coating on low LDPE/D Custom densitypolyethylene difluoroethylene coating on PP/D Custom polypropyleneacetylene plasma coating on PP/A Custom polypropylene acetylene plasmacoating on low LDPE/A Custom density polyethylene polybutyleneterephthalate TPC-ET Hytrel polyether glycol copolymer polyether blockamide TPE PEBA Pebax oxide coated biaxally oriented oxide coated PAHoneywell Nylon Oxyshield Ultra Nanoclay/nylon MXD6/NanoclayImperm/Aegis OXCE Polyethylene PET/SiOx BestPET/ Terephthalate/SiliconeDioxide TechBarrier Polyethylene PET + 02 Scavengers MonoxBarTerephthalate/Oxygen scavengers Modified Polyethylene Modified PETDiamondClear Terephthalate Polyethylene Terephthalate/Nylon 6 PET/MXD6HP867 Amorphous polyvinyl alcohol Amorphous PVOH Nichigo G- PolymerNylon 6/Ethyl vinyl Nylon 6/EVOH/LLDPE Custom alcohol/Linear Low DensityPolyethylene Ethyl vinyl alcohol/Poly- EVOH/PP/EVOH CustomPropylene/Ethyl vinyl alcohol Ethyl vinyl alcohol/Nylon EVOH/NylonCustom Polyethylene/Ethyl vinyl PE/EVOH/PE Custom alcohol/PolyethylenePolyethylene/Ethyl vinyl alcohol/ PE/EVOH/PET Custom PolyethyleneTerephthalate Silicon dioxide-coated PET-SiOx/LLDPE/EVOH/LLDPE CustomPolyethylene Terephthalate/Linear Low Density Polyethylene/Ethyl vinylalcohol/Linear Low Density Polyethylene Aluminum Oxide-coatedPET-Al₂O₃/LLDPE Custom Polyethylene Terephthalate/PolyethylenePolyethylene/Ethyl vinyl PE/EVOH/LLDPE Custom alcohol/Linear Low DensityPolyethylene Polyethylene Terephthalate/ PET/PE/OEVOH/PE CustomPolyethylene/Polyethylene/Bi- axially oriented Ethyl vinyl alcoholPolyethylene Terephthalate/ PET/PE/EVOH/EVOH/EVOH/PE CustomPolyethylene/Ethyl vinyl alcohol/ Ethyl vinyl alcohol/Ethyl vinylalcohol/Polyethylene Polyethylene Terephthalate/ PET/PE/Nylon6/EVOH/Nylon Custom Polyethylene/Nylon 6/Ethyl vinyl 6/PE alcohol/Nylon6/Polyethylene Silicone dioxide-coated PET-SiOx/PE/EVOH/PE CustomPolyethylene Terephthalate/ Polyethylene/Ethyl vinyl alcohol/Polyethylene Polyethylene/Ethyl vinyl PE/EVOH/PVDC Customalcohol/polyvinylchloride Polyethylene Terephthalate/PET/LLDPE/EVOH/LLDPE Custom Linear Low Density Polyethylene/Ethyl vinylalcohol/ Linear Low Density Polyethylene Kurrarister C-coatedPolyethylene PET-Kurrarister-C/PE/EVOH/PE CustomTerephthalate/Polyethylene/Ethyl vinyl alcohol/Polyethylene PolyethyleneTerephthalate/ PET/PE/Nylon 6/EVOH/Nylon Custom Polyethylene/Nylon6/Ethyl vinyl 6/PE alcohol/Nylon 6/Polyethylene Nylon 6/Ethyl vinylalcohol/ Nylon 6/EVOH/PVDC/Nylon Custom Polyvinylchloride/Low Density6/LDPE Polyethylene Polyimide PI Custom Polyimide/Linear Low DensityPI/LLDPE Custom Polyethylene Polyimide/Polyvinylchloride PI/PVdC CustomPolyimide/Polyvinylchloride/ PI/PVdC/LLDPE Custom Linear Low DensityPolyethylene

In particularly preferred embodiments, the composite wall has athickness of 0.005 inches or less (5.0 mil or less); however, in certainembodiments a thicker composite wall may be acceptable. Generally it ispreferred that the composite wall have a thickness of no more than 0.004inches (4.0 mil).

Fabrication of the Balloon

To ensure good mechanical strength of the balloon, the balloon ispreferably thermoformed and sealed such that the edges of the piecesused to form the balloon are overlapping. This can be accomplished byany suitable method. For example, two flat sheets of material can beplaced in a frame with magnetized edges to hold the two sheets in place.Slack can be added to the piece of film to orient the material such thatit maintains its properties after the thermoforming process. The framecan be placed over a mold that represents a hemisphere the balloon. Aheater (e.g., a 4520 watt infrared heater) can be used to form thematerial, and a vacuum can be pulled. The material, with slack put in itprior to vacuum being applied, re-orients the material such that it ismore evenly distributed around the hemisphere shape. The material ispreferably thickest in the middle and is made thinner on the sides whereit will be welded to a second piece to create a sphere or ellipsoidhaving a substantially uniform wall thickness. For example, startingwith a 0.0295″ film, the middle of the film or subsequent apex has anending film thickness of 0.0045″ and the edges have an ending thicknessof 0.0265″ for subsequent overlapping during the welding process.

The valve can be adhered to the (e.g., polyethylene, PE) side of one ofthe hemispheres and protrude out of the opposite (e.g., nylon) side. Onehemisphere typically consists of Nylon as the outermost layer and thesecond hemisphere typically has polyethylene (sealing web) as theoutermost layer. The edges of the two hemispheres are preferably alignedsuch that they overlap by at least 1 mm and no more than 5 mm. Alignmentand overlay of the two hemispheres is done to compensate for thethinning at the edges during the thermoforming process, which in turninhibits seam bursts in vivo. Each half of the spheroid is placed on afixture and the excess from the thermoforming process is trimmed. On amulti-layer film, the sealing layer, a PE or similar layer is bonded tothe sealing layer of the second film half. To do this the film of thehemisphere that has the nylon exposed to the external environment isfolded up along the edges of the sphere on one half such that it can bebonded to the hemisphere with the polyethylene on the outermost layer.

The two film pieces are then sealed using a roller bonder or a bandheater. In the roller bonder, the air provides the compression, theheater provides the sealing heat, and a motor that moves the bonderaround the area controls the time that is required to ensure propersealing. In the band heater, there is a heating element, an expandableplug that provides the compression, and a timer. The band is a metal,preferably copper and a spool-like fixture provides the compressionneeded. Using film layers of different melt temperatures helps ensureintegrity of the barrier layers of the final balloon configuration. Iftwo similar materials are welded, then an insulator can be employed. Ina preferred embodiment, one sphere is provided with the Nylon layerfacing out and the second sphere has a PE layer facing out.

Balloons with Resistance to Spontaneous Deflation

The largest percentage of intragastric balloon malfunctions is due tospontaneous deflations. Spontaneous deflations can occur due to (1)external puncture of the intragastric balloon due to gastric motilityforces, (2) over inflation of the balloon due to increased internalpressure of the balloon from uptake of the gastric environment of thegasses and water vapor and (3) under inflation of the balloon that leadsto fatiguing of the excess material and subsequent puncture of theballoon. By managing these two variables and tuning these variables towithstand the dynamic gastric environment, the balloon system can betailored to ensure it remains inflated throughout its useful life.Instances of spontaneous deflation in this intragastric balloon can beminimized by selection of the starting inflation gas in conjunction withselection of the composite wall materials and construction. Selection ofthe permeability characteristics with respect to water vaportransmission and gas permeability of the composite wall so as to takeadvantage of the properties of the gastric space contents can enable therate of diffusion of gases into and out of the balloon to be controlled.This method allows for a tunable method for prevention of underinflation and over inflation.

Another phenomenon seen with gastric balloons and obesity in general isstomach accommodation. In the process of stomach accommodation, thestomach grows to accommodate the space occupying device or excess foodthat is ingested. In the process of stomach accommodation, the volume ofa stomach containing an intragastric balloon grows over time, such thatthe patient becomes hungrier. However, by controlling gas diffusion andwater vapor transmission across the balloon wall over time, the balloonsize can also be increased over time by selecting the starting inflationgas(es) and water and other in vivo gas permeability characteristics ofthe film so as to maintain weight loss. In addition to spontaneousdeflations, selecting the permeability characteristics of the compositewall in conjunction with the starting gases and utilizing the transferof gases and water inside of the balloon from the gastric environment,the balloon can be designed to grow over its useful life in response tostomach accommodation.

Experiments were performed wherein various starting inflation gases wereselected in conjunction with varying external gas environments thatmimic the stomach gas and water environment in vivo. The stomachenvironment consists of water, acid (hydrochloric acid), a mixture ofgases, and chyme (the semifluid mass of partly digested food expelled bythe stomach into the duodenum). Stomach gas usually arises fromswallowing air during eating. The composition of air is nitrogen (N₂)78.084%; oxygen (O₂) 20.9476%; argon (Ar) 0.934%; carbon dioxide (CO₂)0.0314%; neon (Ne) 0.001818%; methane (CH₄) 0.0002%; helium (He)0.000524%; krypton (Kr) 0.000114%; hydrogen (H₂) 0.00005%; and xenon(Xe) 0.0000087%.

Five gases constitute greater than 99% of the gases in gastrointestinalsystem: N₂, O₂, CO₂, H₂ and methane, with nitrogen predominating.Gastric pCO₂ closely parallels local (splanchnic) arterial and drainingvenous blood pCO₂ values. Neutralization of stomach acid can alsogenerate gas. For example, when the stomach acid reacts withbicarbonates (e.g., as are present in certain antacids) in the digestivejuices, the chemical process creates CO₂, which is normally absorbedinto the blood stream. Digestion of food in the intestines, mainlythrough fermentation by colonic bacteria, generates CO₂, H₂, andmethane. Microbes appear to be the sole source of all of the hydrogenand methane produced in the intestine. These arise from fermentation anddigestion of nutrients (polysaccharides from fruits and vegetables arenot digested in the small intestines). Small quantities of a few othergases, including hydrogen sulfide, indoles, and ammonia can also begenerated.

In certain embodiments, it is preferred that the composition of theinitial fill gas is substantially characteristic of the composition ofthe mixture of gases in the in vivo gastric environment. Such an initialfill gas can include only N₂ and CO₂, or can include only N₂, CO₂, andO₂, or can include N₂ and CO₂ as well as one or more other gases presentin the in vivo environment (e.g., water vapor, H₂, CH₄, Ar, H₂S, orNH₃). Argon or another inert gas (or inert gases) can be substituted inpart or in whole for N₂, which is considered an inert gas in the contextof the preferred embodiments. In those embodiments wherein the fill gasincludes only N₂ or CO₂, it is preferred that the initial fill gascomprises from about 75% v/v to about 96% v/v N₂, from about 5% v/v toabout 15% (vol.) O₂, and from about 1% v/v to about 10% v/v CO₂, morepreferably from about 80% (vol.) to about 85% (vol.) N₂, from about 5%(vol.) to about 13% (vol.) O₂, and from about 4% (vol.) to about 8%(vol.) CO₂. In those embodiments wherein the fill gas includes only N₂or CO₂, it is preferred that the initial fill gas comprises from about4% (vol.) to about 8% (vol.) CO₂, with the remainder N₂ or another inertgas. In embodiments wherein the initial fill gas comprises other gasesin addition to CO₂ and the inert gas(es), it is preferred that theinitial fill gas comprises from about 4% (vol.) to about 8% (vol.) CO₂.

Controlled self-inflation of the intragastric balloon in the in vivoenvironment can be achieved by using a semi-permeable or permeablecomposite wall in the balloon and initially filling the balloon with apreselected single gas, such as N₂ or O₂. The balloon utilizesdifferences in concentrations of gases and water concentrationdifferences between the internal balloon environment and the externalenvironment in vivo (GI/stomach) to increase and/or decrease the volumeand/or pressure over time. To achieve a controlled decrease in volumeand/or pressure, a wall can be employed that has a relatively higherpermeability to the single gas used to inflate the balloon than to othergases present in the in vivo gastrointestinal environment. For example,if nitrogen gas is employed as the inflation gas, over time in the invivo environment, the volume and/or pressure in the balloon willdecrease as nitrogen diffuses out into the in vivo environment throughthe oxygen permeable wall. Similarly, if oxygen gas is employed as theinflation gas, over time in the in vivo environment, the volume and/orpressure in the balloon will decrease as oxygen diffuses out into the invivo environment through the oxygen permeable wall. The differential inpartial pressure of the single gas in the balloon (higher) versus the invivo environment (lower) will drive the process until equilibrium orhomeostasis is reached. To achieve a controlled increase in volumeand/or pressure, a wall can be employed that has a relatively lowerpermeability to the single gas used to inflate the balloon than to othergases present in the in vivo gastrointestinal environment. For example,if nitrogen gas is employed as the inflation gas, over time in the invivo environment, the volume and/or pressure in the balloon willincrease as CO₂, and all of the other gases present in the gastricenvironment, diffuse into the balloon through the CO₂ permeable wall.The differential in partial pressure of the permeable gas in the balloon(lower) versus the in vivo environment (higher) will drive the processuntil equilibrium is reached.

In addition, maintaining and/or controlling inflation of the balloon canalso be done using the differences in concentrations between theinternal balloon environment and external gastric environment in whichthe balloon volume/pressure can be increased or decreased as needed toextend the useful life of the product. One reason to decrease thepressure can be to first inflate the balloon with a large, but highlydiffusible/soluble gas molecule such as CO₂ in addition to a more inertgas like nitrogen to pre-stretch the balloon, with the soluble gasdiffusing out of the balloon and other gases not originally present inthe balloon migrating in to fill the balloon.

Inflation gases can be selected to start with the majority of the gas inthe balloon comprising a large, inert gas or a gas that has lowdiffusivity through the selected composite wall. Examples of inert gasesinclude but are not limited to nitrogen, as well as SF₆, C₂F₆, C₃F₈,C₄F₁₀, C₄F₈, C₄F₈, C₃F₆, CF₄, and CCl F²⁻CF₃. An inert gas inconjunction with a less inert gas(es) that are more soluble in thegastric environment, can be combined to comprise the starting ballooninflation gas composition where the inert gas would be in excess to themore soluble/diffusible gas. Patient diet and medications can alsoaffect/control balloon inflation status—primarily by CO₂ concentrationeffects produced in the gastric environment. In addition, gastric pHalso affects CO₂ concentration. This particular method can also allowfor a greater degree of tuning of the device's useful life based on thecomposite wall material, e.g., barrier/non-barrier and whether the gasthat diffuses in is maintained longer in the balloon if it has a barrierwall versus a non-barrier wall. This particular form of self-inflationcan be employed using a self-inflating gastric balloon (e.g., initiallyinflated by a gas generating reaction in the balloon initiated afterswallowing), or an inflatable gastric balloon (e.g., inflated using acatheter, with or without endoscopic assistance, deliverednasogastrically or any other delivery method). The method can be usedwith any gastric balloon, including swallowable balloons and balloonsplaced in the stomach by, e.g., endoscopic methods. The method isparticularly preferred for use in connection with intragastric devices;however, it can also be applied to use in, e.g., pulmonary wedgecatheters and urinary incontinence balloon devices. The advantages tothis technology include the ability to compensate for stomachaccommodation, allowing the balloon to adapt to a stomach that mayincrease in volume over time, thereby maintaining patient satiety. Italso permits starting with a smaller amount of inflation gasconstituents for a self-inflating balloon. It can prevent spontaneousdeflations by utilizing diffusion gradients between gastric balloonsystems and the in vivo gastric environment.

In some embodiments, one or more liquids are used as an inflation agent.Liquids suitable for use as an inflation agent include, but are notlimited to pure water, saline solution, and liquid forms of thepreviously described inflation gases such as SF₆, C₂F₆, C₃F₈, C₄F₁₀,C₄F₈, C₄F₈, C₃F₆, CF₄, CCl F²⁻CF₃, and combinations thereof. In someembodiments, the inflation agent can include a mixture of one or moreinflation liquids and one or more inflation gases. The inflation agentcan include between less than 10% and greater than 90% liquid. In someembodiments, the inflation agent can include between 10% and 30%,between 30% and 60%, or between 60% and 90% liquid. In some embodiments,the inflation agent can include 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%,and 90% liquid. In certain embodiments, it is preferred that thecomposition of the inflation agents is substantially characteristic ofthe composition of the mixture of gases in the in vivo gastricenvironment.

The volume-occupying subcomponent can be constructed of a polymericsubstance such as polyurethane, polyethylene terephthalate, polyethylenenaphthalate, polyvinyl chloride (PVC), Nylon 6, Nylon 12, or polyetherblock amide (PEBA). In some preferred embodiments used in connectionwith inflation agents including an inflation liquid, thevolume-occupying subcomponent consists entirely or primarily ofsilicone. However, any suitable biocompatible material capable ofwithstanding the gastric environment and strong enough to hold theinflation agent may be used. Examples of such materials are listed inTables 1a-b and 2. In some embodiments, the volume-occupyingsubcomponent includes materials that are expandable. In a particularlypreferred embodiment hying an expandable volume-occupying subcomponentSF₆ is used as the inflation agent. SF₆ expands at a defined rate,allowing for control over the rate of balloon expansion, the finalexpanded balloon size, and the length of time it takes to achieve thedesired final size.

In a particularly preferred embodiment, used in connection with N₂ (withor without CO₂) as the inflation agent, a multi-layer co-extruded blendfor the wall layers is employed. A particularly preferred configurationis Nylon 12/Ethyl Methyl Acrylate/Polyvinylidene Chloride/Ethyl MethylAcrylate/Nylon 12/Linear Low Density Polyethylene+Low DensityPolyethylene (also referred to as co-extruded Nylon 12-encapsulatedPVDC-Nylon 12-LLDPE+LDPE multilayer). Another particularly preferredconfiguration is a co-extruded multi-layer Nylon 12/Linear Low DensityPolyethylene+Low Density Polyethylene. Selection of the resins for thecomposite wall construction (as well as selection of using a coextrusionmethod or adhesives) can be varied to control compliance (stretchiness),puncture resistance, thickness, adhesion, sealing bond strength,orientation, acid resistance, and permeability characteristics to gassesand water vapor to achieve a particular effect.

Automatic Deflation of Intragastric Balloon Systems

The self-inflating (also referred to as automatic inflating) orinflatable (also referred to as manually inflating) intragastric balloonis provided with mechanisms to reliably control timing of deflation. Inpreferred embodiments, the balloon auto-deflates and passes through thestomach, through the lower gastrointestinal tract, and out of the bodyat the end of its pre-determined useful life (non-spontaneous),preferably between 30 and 90 days but can be timed to deflate within 6months. In the preferred embodiments described below, the timing ofdeflation can be accomplished via the external gastric environment (byconditions of temperature, humidity, solubility, and/or pH, for example)or via the environment within the lumen of the inflated balloon. It ispreferable for consistency to control the initiation of theself-deflation process by manipulating the internal balloon environment.

In other embodiments, the patch applied to allow for inverted seams asdescribed above and/or one or more additional patches or otherstructures added to the balloon construction are made out of anerodible, degradable, or dissolvable material (natural or synthetic) andare incorporated into the wall of the balloon. The patch(s) are ofsufficient size to ensure opening of a sufficient surface area to causerapid deflation, and to prevent re-inflation by seepage of stomach fluidinto the balloon. The balloon patch(s) comprise materials that can beapplied to the balloon such that a substantially smooth surface ismaintained, and preferably comprise a single layer or multi-layeredmaterial. The patch(s) are constructed using an erodible, disintegrable,degradable or other such material that is preferably tissue-compatibleand degrades into non-toxic products or is a material that slowlyhydrolyzes and/or dissolves over time (e.g., poly(lactic-co-glycolicacid) (PLGA), poly(lactide-co-glycolide) (PLG), polyglycolic acid (PGA),polycaprolactone (PCL), polyesteramide (PEA), polyhydroxyalkanoate(PHBV), polybutylene succinate adipate (PBSA), aromatic copolyesters(PBAT), poly(lactide-co-caprolactone) (PLCL), polyvinyl alcohol (PVOH),polylactic acid (PLA), poly-L-lactic acid PLAA, pullulan, polyethyleneglycol (PEG), polyanhydrides, polyorthoesters, polyaryletherketones(PEEK), multi-block polyetheresters, poliglecaprone, polydioxanone,polytrimethylene carbonate, and other similar materials). Theseerodible, disintegrable, or degradable materials can be used alone, orin combination with other materials, or can be cast into/co-extruded,laminated, and/or dip coated in conjunction with non-erodible polymers(e.g., PET or the like) and employed in the construction of the balloon.Degradation/erosion occurs, is initiated by, and/or is controlled by thegastric environment (e.g., by conditions of temperature, humidity,solubility, and/or pH, for example), or is controlled within the lumenof the balloon (e.g., by conditions of humidity and/or derived pH, forexample) based on what the patch is exposed to. Thickness of the polymeras well as environment which affects degradation and time of exposurecan also facilitate degradation timing. Degradation/erosion are timedsuch that they occur once the pre-determined balloon useful life iscompleted (e.g., inflation is maintained for from 25 to 90 days in vivoin the stomach before degradation/erosion results in formation of anopening permitting deflation). As an alternative to (or in connectionwith) using an degradable material for the patch, the patch can comprisea similar fluid retention barrier film or the same film as the remainingwall of the balloon which is adhered to the balloon using a weakadhesive, or welded or adhered such that after a specified amount oftime the patch delaminates from the applied area and allows for anopening for inflation fluid release for deflation. Or if deemednecessary for rapid deflation the entire balloon composite wall can bemade of the erodible material. The mechanism of using an erodiblematerial or a material that mechanically fails after a pre-specifiedtime is be similar for all embodiments for deflation mechanismsdescribed below as well. The timing of degradation or erosion can becontrolled using the external gastric environment (e.g., by conditionsof temperature, humidity, solubility, and/or pH, for example) and/or canbe controlled by conditions within the lumen of the balloon (e.g., byconditions of humidity and/or pH of residual liquid in the balloon).

In other embodiments, a plug or plugs (optionally in conjunction anotherdegradable retaining structure) can be incorporated into the balloonconstruction and can consist, all or in part, of an erodible,disintegrable, or otherwise degradable synthetic or natural polymersimilar to those described above (e.g., PLGA, PLAA, PEG, or the like).The plug can be formed into various shapes (e.g., cylinder shape) toachieve various surface-to-volume ratios so as to provide a preselectedand predictable bulk degradation pattern for the erodible polymer. Theplug can incorporate a releasing mechanism that can be chemicallyinitiated after degradation/erosion begins, such that the septum or plugmaterial pops out of the balloon or falls inside of the balloon, therebycreating a passageway for fluid release and subsequent deflation of theballoon. Mechanical additions that can be used in conjunction with aplug include a degradable/erodible/disintegrable material that holds aplug (e.g., of a non-degradable or degradable material) in place or acompressed spring housed within the retaining structure or plugstructure. More specifically one preferred embodiment to achievedeflation can comprise a housing, a radial seal, a solid eroding core,and a protective film attached to the external surface of the erodingcore. The inside of the eroding core is exposed to the internal balloonliquid. The core creates a compressive force that holds the seal againstthe housing. As the core erodes, the compression between the housing andthe radial seal is reduced until there is clearance between the housingand the seal. Once there is clearance, gas can move freely from theinside of the balloon to the outside environment. The seal can fall outof the housing and into the balloon. The diameter, length, and materialtypes can be adjusted in order to create the deflation at a desired timepoint. Example materials for each component used to achieve thisdeflation mechanism can be as follows: Housing: Biocompatible structuralmaterial, capable of withstanding enough radial force to form an airtight seal. Possible materials include: polyethylene, polypropylene,polyurethane, UHMWPE, titanium, stainless steel, cobalt chrome, PEEK, ornylon; Radial Seal: The radial seal needs to be composed of abiocompatible elastic material, capable of providing liquid and gasbarrier to acidic environments. Possible materials include: silicon,polyurethane, and latex; Eroding Core: The eroding core needs to be amaterial capable of breaking down at a predictable rate at givenenvironmental conditions. Possible materials include: PLGA, PLA, orother polyanhydrides that are capable of losing integrity over time orany materials listed above that provide erodible characteristics.

For the spring mechanism, once the material degrades, the spring isreleased and/or the plug/septum is pulled into the balloon or pushed outof the balloon, thus releasing fluid once an orifice has been created byrelease of the spring mechanism and pushing out or pulling in of theplug.

Another preferred embodiment is comprised of a septum, moisture erodingmaterial inside an inlet port, and moisture absorbing expansionmaterial. The eroding materials slowly erode away when exposed tomoisture, eventually exposing the moisture absorbing expansion material.When the moisture expanding material begins to absorb moisture, theexpansion pulls the septum out of position in the head by pushingagainst a septum lip or a ring attached to the septum. Pulling theseptum out of position causes an immediate deflation of the balloon. Inorder to protect the expanding material from moisture until a desiredtimepoint, the expanding material can be sheathed in water blockingmaterials, such as parylene, as well as slowly water degradingmaterials. The moisture contact can be controlled by small inlet ports.The inlet ports can be small holes, or a wick material that drawsmoisture in a controlled manner. The desired deflation time is achievedthrough a combination of eroding materials, blocking materials, andinlet port sizing.

In certain embodiments, the balloon can incorporate one or more plugs inthe wall of the balloon that contain a compressed pellet or gasreleasing pellet. The pellet can be comprised of any combination ofconstituents that, when activated, emit CO₂ gas (e.g., sodiumbicarbonate and citric acid, or potassium bicarbonate and citric acid,or the like). The pellet can be in tablet or rod form protected by anerodible, disintegrable, or degradable material that is preferablytissue-compatible and degrades into non-toxic products or that slowlyhydrolyzes and/or dissolves similarly to the plugs and patches describedabove (e.g., poly(lactic-co-glycolic acid) (PLGA), polyvinyl alcohol(PVOH), polylactic acid (PLA), poly-L-lactic acid PLAA, Pullulan,Polyethylene Glycol, polyanhydrides, polyorthoesters,polyaryletherketones (PEEK), multi-block polyetheresters,poliglecaprone, polydioxanone, polytrimethylene carbonate, and otherlike materials). Degradation/erosion of the plug initiates the reactionof the two chemicals in the pellet and subsequently leads to formationof gas (e.g., CO₂). As sufficient gas is trapped or built up, sufficientpressure is eventually generated to push out the softened polymermaterial and create a larger channel for the CO₂ gas in the balloon toescape. External pressure applied by the stomach to the balloon (e.g.,squeezing) can contribute to the process of creating a larger channel.Dimensions and properties of the plug (diameter, thickness, composition,molecular weight, etc.) comprised of the polymer drives the timing ofdegradation.

In other embodiments, plugs or patches of different shapes or sizessimilar to those of the plugs described above can be employed within theballoon lumen in a multi-layer configuration including a semi-permeablemembrane to facilitate balloon deflation. The plug or patch is made ofsimilar degradable/erodible/dissolvable material as described above(e.g., poly(lactic-co-glycolic acid) (PLGA), polyvinyl alcohol (PVOH),polylactic acid (PLA), PLAA, pullulan, and other like materials) andcontains a compartment enclosed by a semi-permeable membrane(impermeable to an osmolyte) that contains a concentrated solution of asolute or osmolyte (such as glucose, sucrose, other sugars, salts, orcombination thereof). Once the plug or patch begins to degrade or erode,the water molecules move by osmosis down the water gradient from theregion of greater water concentration to the region of lower waterconcentration across the semi-permeable membrane into the hypertonicsolution in the compartment. The compartment containing the osmolyteswells and eventually bursts, pushing the membranes and the degradedplug or patch out, thereby allowing rapid gas loss through the newlycreated channels or areas.

In certain embodiments, a balloon composed of a septum, moisture erodingmaterial inside an inlet port, and moisture absorbing expansion materialis employed. The eroding materials slowly erode away when exposed tomoisture, eventually exposing the moisture absorbing expansion material.When the moisture expanding material begins to absorb moisture, theexpansion pulls the septum out of position in the head by pushingagainst a septum lip or a ring attached to the septum. Pulling theseptum out of position causes an immediate deflation of the balloon. Inorder to protect the expanding material from moisture until a desiredtime point has been reached, the expanding material can be sheathed inwater blocking materials, such as parylene, as well as slowly waterdegrading materials. The moisture contact can be controlled by smallinlet ports. The inlet ports can be small holes, or a wick material thatdraws moisture in a controlled manner. The desired deflation time isachieved through a combination of eroding materials, blocking materials,and inlet port sizing.

Another mechanism for self-deflation is to create a forced de-laminationscheme, which can provide a larger surface area to ensure rapiddeflation. In, e.g., a balloon having a tri-layer wall, the outermostlayer is substantially strong enough to hold the inflation fluid (e.g.,polyethylene terephthalate (PET) or the like), the middle layer iscomprised entirely of an erodible material (e.g., PVOH or the like)while the inner layer is comprised of a weaker material (e.g.,polyethylene (PE) or the like). The PET or outermost layer is “scored”or hatched with erodible material to create small channels that erodeover time. This creates channels such that the gastric fluid seeps intothe balloon layers and starts degrading the fully erodible material.When the erodible layer degrades or dissolves, the material thatcomposes the innermost layer also erodes, degrades or dissolves since itis not strong enough to withstand the gastric forces/environment on itsown. The balloon then collapses on itself and eventually passes throughthe lower gastrointestinal tract. Having an erodible layer sandwichedbetween a strong and weak layer facilitates timing of erosion bycreating a longer path length than an erodible plug or patch affected bythe gastric environment. The distance between scores or openings canalso be selected so as to provide a desired deflation rate.

In another embodiment providing abrupt deflation of the balloon after adesired period of time has elapsed, the composite wall of the entireballoon or a section of the composite wall (patch) includes severalmaterial layers that are slowly penetrated by water that has beeninjected inside the balloon during the manufacturing process or duringthe inflation process. This water penetrates through the layers,eventually reaching a material that substantially expands, rupturing athin external protective later, and creating a large hole for gas toescape and the balloon to deflate. The water expanding material isprotected from liquid via a coating or sheath, such as parylene, whichallows a controllable amount of moisture exposure. Once water reachesthe expansion material, it exerts a force on the protective outer layer,causing it to rupture. The outer layer may be created with a weakenedbonding area, a partially scored area, or other methods of ensuring adesired rupture location and to facilitate desired timing forauto-deflation to take place. There can be any number of layers betweenthe moist environment and the moisture expanding center. Each materiallayer can have different erosion rates (e.g., fast or slow) and can beselected by the predetermined time deflation is desired to occur (e.g.,after 30 days, 60 days, or more). By varying the number, thickness, andrate of each of the circumferential layers, the time to deflation can beaccurately controlled.

Alternatively a pressure sealing button that is adhesively bonded over aperforation in the balloon material can be provided for deflation. Theadhesive bonding the button erodes over time when it comes into contactwith moisture derived from the gastric fluid or that has been injectedinside the balloon. Once the adhesive can no longer bond and create anairtight seal between the adhesive and the button, the balloon willrapidly deflate. By controlling the hole size and moisture exposure ofthe adhesive, the erosion time can be accurately predicted.

Deflation can also be facilitated by creating a series of connectingports within the septum or on another similar structure attached to theballoon composite wall. The ports can be constructed using a water- oracid-dissolving, biologically compatible, low permeability substance,such as gelatin. The diameter of the hole, number of holes, channelwidth, and channel length can all be adjusted to control the dissolvingparameters. Once the material in the ports and channel is dissolved,there is a clear path for gas trapped in the balloon to escape,eventually resulting in a deflated balloon. The water can be gastricfluid or controlled internally by including water inside the balloon atassembly or during the inflation process. There can be a plurality ofport openings to guarantee gas transmits. Additionally, there areseveral variables that can be adjusted to control dissolution time: sizeof the port openings; number of port openings; the length of theinternal channel; the width of the internal channel; and the rate ofmaterial dissolution. The port/channel layout design can ensure thatonly a small amount of surface area is exposed to moisture at anyparticular time, thereby controlling the rate of erosion and ultimatelydeflation.

A mechanism to facilitate passing involves an erosion mechanism thatallows for the balloon to be broken down into a size that has a higherprobability of predictably passing through the lower gastrointestinalsystem. Preferably, the size of the balloon as deflated is less than 5cm long and 2 cm thick (similar to various foreign objects of similarsize that have been shown to pass predictably and easily through thepyloric sphincter). This can be accomplished by providing the balloonwith “erodible seams.” One seam that breaks the balloon open into (at aminimum) two halves, or more seams are provided so that a plurality ofsmaller balloon pieces is produced in the dissociation reaction. Thenumber of seams used can be selected based on the original surface areaof the balloon and what is required to dissociate the balloon intopieces that are of a size that can predictably pass through thegastrointestinal tract more easily. The rate of seam erosion can becontrolled by using a material affected by, e.g., the external gastricenvironment pH, liquid, humidity, temperature, or a combination thereof.Seams can be single layer consisting of only erodible material, ormulti-layer. The timing of self-deflation can be further controlled bythe design of the seam layers, e.g., making the reaction and/ordegradation of the seam material dependent on the internal environmentof the balloon instead of the external environment. By manipulating thereaction such that erosion or degradation is initiated by the internalenvironment (e.g., the balloon's internal pH, humidity, or otherfactors), any impact of person-to-person gastric variability (pH, etc.)that can affect erosion timing is minimized. The internal balloonenvironment can be manipulated by adding excess water at injection tocreate a more humid internal environment, or the amount of constituentsadded can be varied to manipulate the pH, etc.

EXAMPLES Film Permeability

A variety of different composite films were tested for permeability ofgases as measured by CO₂ diffusion at 37° C. As shown in the data ofTable 3, the permeability of varying composite wall constructions wereevaluated and determined by their resistance to CO₂ diffusion rates,where the smaller the permeability test result, the higher barrier togas diffusion the film provides. As noted, the permeability of the filmand degree of barrier the film provides to gas diffusion was derivedusing CO₂ at 37° C., one of the most permeable gasses. This can be usedas a surrogate to other gas diffusion rates where generally CO₂ is 3 to5 times faster in diffusion across a membrane than oxygen, and nitrogenis 0.2 to 0.4 times faster than the oxygen transmission rate when theseare evaluated at 25° C. As Table 3 indicates, permeability of the filmis also affected by orientation of the film (which layer is exposed tothe CO₂ gas first), and Relative Humidity. The walls were tested underconditions of low relative humidity (0%, representative of conditionsinside the balloon upon fill) and high relative humidity (100%,representative of in vivo conditions). In certain embodiments, acomposite wall having a permeability of <10 cc/m²/day is generallypreferred; however, depending upon the desired effect of inflation andre-inflation by in vivo gasses such as CO₂, a higher permeability of >10cc/m²/day in in vivo conditions can be desirable. For example, each ofthe films in the table can be suitable for use in various selectedembodiments, such that the resulting balloon wall has a permeability toCO₂ of even greater than >10 cc/m²/day, e.g., >50 cc/m²/day, >100cc/m²/day, >200 cc/m²/day, >300 cc/m²/day, >400 cc/m²/day, >500cc/m²/day, >750 cc/m²/day, >1000 cc/m²/day, >1500 cc/m²/day, >2000cc/m²/day, >2500 cc/m²/day, >3000 cc/m²/day, >3500 cc/m²/day, oreven >4000 cc/m²/day. In selected embodiments, it is generally preferredto have a permeability of from about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10cc/m²/day to about 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100,110, 120, 130, 140 or 150 cc/m²/day.

TABLE 3 Innermost Permeability Film Layer (CO Test Results ThicknessExposed (cc/m/day) Film (in) Layer) RH % (ATM/° C.) PE/EVOH/PE 0.002 ±0.001 PE 0 10.8 70% Nylon 6,66, 0.003 Nylon 6,66 0 2.4 30% MXD6/EVOH/PVDC/ 70% Nylon 6,66, 30% MXD6/ LLDPE + LDPE 70% Nylon 6,66, 0.003Nylon 6,66 95 ± 5 51.0 30% MXD6/ EVOH/PVDC/ 70% Nylon 6,66, 30% MXD6/LLDPE + LDPE 70% Nylon 6,66, 0.003 LDPE 95 ± 5 3.3 30% MXD6/ EVOH/PVDC/70% Nylon 6,66, 30% MXD6/ LLDPE + LDPE 70% Nylon 6,66, 0.002 LDPE 0 43.030% MXD6/PVDC/ 70% Nylon 6,66, 30% MXD6/ LLDPE + LDPE 70% Nylon 6,66,0.003 LDPE 0 50.0 30% MXD6/PVDC/ 70% Nylon 6,66, 30% MXD6/ LLDPE + LDPE70% Nylon 6,66, 0.002 LDPE 95 ± 5 41.0 30% MXD6/PVDC/ 70% Nylon 6,66,30% MXD6/ LLDPE + LDPE 70% Nylon 6,66, 0.003 LDPE 95 ± 5 49.0 30%MXD6/PVDC/70% Nylon 6,66, 30% MXD6/LLDPE + LDPE Bi-axially Oriented0.00125 LDPE 0 15.4 PP/EVOH/PE Bi-axially Oriented 0.00175 PE 0 8.2PP/EVOH/PE Bi-axially Oriented 0.00125 PE 95 ± 5 282.6 PP/EVOH/PEBi-axially Oriented 0.00125 PE 95 ± 5 1088.0 PP/EVOH/PE Bi-axiallyOriented 0.00175 PE 95 ± 5 235.4 PP/EVOH/PE Cast PP 0.002 ± 0.001 NA 0772.0 Cast PP/PE/EVOH/PE 0.0025 PE 0 7.2 Cast PP/PE/EVOH/PE 0.0025 PE 010.1 Cast PP/PE/EVOH/PE 0.0025 PE 95 ± 5 169.3 Cast PP/PE/EVOH/PE 0.0025PE 95 ± 5 18.5 Coextruded 0.00125 PE 0 8.1 PE/EVOH/PE Coextruded 0.0015PE 0 4.9 PE/EVOH/PE Coextruded PET/SiOx/PE 0.002 ± 0.001 PE 0 12.4CoExtrude- 0.0025 HDPE 0 1.7 LLDPE/HDPE/EVOH/HDPE HDPE/HDPE/PVdC/ 0.003HDPE 0 5.0 EVOH/HDPE/ LLDPE + LDPE HDPE/HDPE/PVdC/ 0.003 HDPE 95 ± 5 6.8EVOH/HDPE/ LLDPE + LDPE HDPE/HDPE/PVdC/ 0.003 LDPE 0 4.4 EVOH/HDPE/LLDPE + LDPE HDPE/HDPE/PVdC/ 0.003 LDPE 95 ± 5 52.0 EVOH/HDPE/ LLDPE +LDPE HDPE/HDPE/PVdC/ 0.003 LDPE 0 74.0 HDPE/HDPE/ LLDPE + LDPEHDPE/HDPE/PVdC/ 0.003 LDPE 0 47.0 HDPE/HDPE/ LLDPE + LDPEHDPE/HDPE/PVdC/ 0.003 LDPE 95 ± 5 68.0 HDPE/HDPE/ LLDPE + LDPEHDPE/HDPE/PVdC/ 0.003 LDPE 95 ± 5 44.0 HDPE/HDPE/ LLDPE + LDPEKurarister ™ C, 3 mil 0.003 UNK 0 3.2 Nylon12/PvDC/Nylon12/ 0.003LLDPE + LDPE 0 52.0 LLDPE + LDPE Nylon12/PvDC/Nylon12/ 0.003 LLDPE +LDPE 95 ± 5 56.0 LLDPE + LDPE MPI Supernyl 0.0022 LLDPE 0 3.3 LLDPE 40μm MPI Supernyl 0.0022 LLDPE 95 ± 5 5.8 LLDPE 40 μm MPI Supernyl 0.0026LLDPE 0 4.2 LLDPE 50 μm MPI Supernyl 0.0026 LLDPE 95 ± 5 7.5 LLDPE 50 μmNylon12/PvDC/Nylon12/ 0.003 LLDPE + LDPE 0 59.3 LLDPE + LDPENylon12/PVDC/ 0.003 LLDPE + LDPE 95 ± 5 29.5 Nylon12/ LLDPE + LDPENylon12/PVDC/ 0.003 LLDPE + LDPE 0 73.2 Nylon12/ LLDPE + LDPE-Thermoformed Nylon12/PVDC/ 0.0024 LLDPE + LDPE 0 77.0 Nylon12/ LLDPE +LDPE Nylon12/PVDC/ 0.0024 LLDPE + LDPE 95 ± 5 68.0 Nylon12/ LLDPE + LDPENylon12/PVdC/ 0.003 LDPE 0 58.0 Nylon12/LDPE-Cast Nylon12/Nylon Tie/0.003 LDPE 95 ± 5 54.0 EVA/PVdC/Adhesive/ Nylon12/Nylon Tie/ LDPE-CastNylon12/PVdC/ 0.0035 LDPE 0 14.9 Nylon12/LDPE Nylon12/ 0.004 LDPE 0 34.0PVdC/Nylon12/ LDPE Nylon12/ 0.0035 LDPE 95 ± 5 24.9 PVdC/Nylon12/ LDPENylon12/ 0.0035 LDPE 95 ± 5 41.3 PVdC/Nylon12/ LDPE Nylon12/ 0.004 LDPE95 ± 5 31.7 PVdC/Nylon12/ LDPE Nylon 6,66/ 0.0024 LDPE 0 54.0PVDC/Nylon6,66/ LLDPE + LDPE Nylon 6,66/ 0.0024 LDPE 95 ± 5 56.0PVDC/Nylon6,66/ LLDPE + LDPE Nylon 6,66/ 0.0032 LDPE 0 5.5 EVOH/PVDC/Nylon 6,66/LDPE Nylon 6,66/ 0.0032 LDPE 95 ± 5 6.4 EVOH/PVDC/ Nylon6,66/LDPE Nylon 6,66/ 0.0032 Nylon 6, 66 95 ± 5 49.9 EVOH/PVDC/ Nylon6,66/LDPE Nylon 6,66/ 0.0027 LDPE 0 57.0 PVDC/Nylon6,66/ LLDPE + LDPENylon 6,66/ 0.003 LDPE 0 41.0 PVDC/Nylon6,66/ LLDPE + LDPE Nylon 6,66/0.0027 LDPE 95 ± 5 55.0 PVDC/Nylon6,66/ LLDPE + LDPE Nylon 6,66/ 0.003LDPE 95 ± 5 46.0 PVDC/Nylon6,66/ LLDPE + LDPE Multi-layer Nylon 12/0.0035 LDPE 0 3203.5 LLDPE + LDPE Multi-layer Nylon 12/ 0.004 LDPE 02725.5 LLDPE + LDPE Multi-layer Nylon 12/ 0.0045 LDPE 0 2553.6 LLDPE +LDPE Multi-layer Nylon 12/ 0.0035 LDPE 95 ± 5 2539.3 LLDPE + LDPEMulti-layer Nylon 12/ 0.004 LDPE 95 ± 5 2527.8 LLDPE + LDPE Multi-layerNylon 12/ 0.0045 LDPE 0 1522.6 LLDPE + LDPE + Parylene Multi-layer Nylon12/ 0.0045 LDPE 95 ± 5 1275.5 LLDPE + LDPE + Parylene NYLON-SIOX/HDPE/0.003 LLDPE 95 ± 5 83.0 LLDPE NYLON- 0.003 LLDPE 0 70.0 SIOX/HDPE/LLDPENylon-SIOX/LLDPE 0.0015 LLDPE 0 134.0 Nylon-SIOX/LLDPE 0.0015 LLDPE 95 ±5 82.0 OPP Co-extrude with 0.002 mPE 0 5.9 mPE/EVOH/mPE OPP Laminated to0.0025 mPE 0 4.7 mPE/EVOH/mPE OPP Laminated to 0.003 mPE 0 3.4mPE/EVOH/mPE OPP Laminated to 0.0025 mPE 95 ± 5 294.3 mPE/EVOH/mPE OPPSIOX/LLDPE 0.002 LLDPE 0 540.5 OPP SIOX/LLDPE 0.002 LLDPE 0 1081.0 OPPSIOX/LLDPE 0.002 LLDPE 95 ± 5 565.0 OPP SIOX/LLDPE 0.002 LLDPE 95 ± 5594.5 OPP/mPE/ 0.0021 mPE 0 5.0 EVOH/mPE OPP/mPE/ 0.0021 mPE 95 ± 5437.1 EVOH/mPE OPP/PE/ 0.0025 OPP 0 8.5 EVOH/PE OPP/PE/ 0.0025 OPP 95 ±5 11.6 EVOH/PE OPP/PE/ 0.00175 PE 0 8.1 EVOH/PE OPP/PE/ 0.0025 PE 0 8.9EVOH/PE OPP/PE/ 0.0025 PE 0 18.6 EVOH/PE OPP/PE/ 0.0025 PE 95 ± 5 259.0EVOH/PE OPP/PE/ 0.0025 PE 95 ± 5 556.1 EVOH/PE OPP/PVDC/mPE 0.0017 mPE 074.2 OPP/PVDC/mPE 0.0017 mPE 95 ± 5 84.6 OPP-SIOX/LLDPE 0.002 ± 0.001LLDPE 95 ± 5 1159.7 Oriented PA 0.002 ± 0.001 NA 0 750.9 Oriented PP0.002 ± 0.001 NA 0 726.0 PA/EVOH/ 0.0022 LLDPE 0 5.0 PA/LLDPE PA/EVOH/0.0022 LLDPE 0 3.1 PA/LLDPE PA/EVOH/ 0.0022 LLDPE 95 ± 5 10.8 PA/LLDPEPE/EVOH/PE 0.002 ± 0.001 PE 0 9.2 PET 0.001 PE 0 524.7 SiOx-PET/EVOH/PE0.002 PE 0 1.4 SiOx-PET/MPE/ 0.0016 mPE 0 1.0 EVOH/mPE Si-Ox-PET/PE/0.00125 PE 0 1.7 EVOH/PE Si-Ox-PET/PE/ 0.0015 PE 0 1.6 EVOH/PESi-Ox-PET/PE/ 0.0015 PE 0 5.4 EVOH/PE Si-Ox-PET/PE/ 0.002 PE 0 1.5EVOH/PE Si-Ox-PET/PE/ 0.002 PE 0 1.8 EVOH/PE Si-Ox-PET/PE/ 0.002 PE 95 ±5 22.6 EVOH/PE

Animal Studies

Two different composite walls were tested: a material(Nylon12/PvDC/Nylon 12/LLDPE+LDPE) with high barrier materialcharacteristics and a material with low barrier characteristics(multi-layer Nylon12/LLDPE+LDPE). A series of experiments were performedusing a mixture of 75% N₂ and 25% CO₂ as the balloon initial fill. Asshown in the data of Table 4, each of the balloons maintained pressureover the duration tested, but gained substantially in volume.Considering the composite walls studied are not a metal canister (volumeand pressure change due to material stretch) there was a significantchange in the number of overall gas molecules inside the balloon fromthe initial gas fill. Since the internal balloon environment startedwith CO₂ and nitrogen, most likely additional CO₂ entered due to theenvironment the balloon was subjected to (N₂ and CO₂ headspace) but alsomost likely other gases available in the air as well as water vapor alsodiffused within the balloon wall.

TABLE 4 % CO₂ in Starting balloon Measured Balloon #, implant Estd.Explant Explant (meas. w/ % CO₂ in % gas Pig Wall pressure Volume VolumePressure CO₂ stomach Final gain # Composition (PSI) at implant (cc)(PSI) meter) gas (%) Vol. (calc.) 1 1, Barrier 1.0 277 360 1.1   22% 10%385 23.5 Material (Nylon/Saran) 1 2, Barrier 1.09 282 340 0.7 19.63% 10%358 15 Material (Nylon/Saran) 2 3, Non- 1.15 283 330 1.2 26.57%  8% 32014.5 Barrier Material (Nylon) 2 4, Non- 1.07 281 323 0.96   31%  8% 31612.4 Barrier Material (Nylon)

Volume gains were higher for the barrier material composite walls thanfor the non-barrier walls. An analysis of gas in the balloons afterexplants (Tables 5a and 5b) showed gains in oxygen, hydrogen, and argonin addition to the nitrogen and carbon dioxide that was already presentin the balloon at initial inflation. The balloons, both with a goodbarrier composite wall (table 5a) and a poor barrier composite wall(table 5b) both gained in overall volume while maintaining pressureafter 30 days in vivo. Explant results of the balloon with a compositewall containing a good barrier material (#2, table 5a) showed a slightlyhigher increase in carbon dioxide than the wall without a barriermaterial (#3, table 5b). It is unlikely that nitrogen diffused in or outof the balloon due to its inertness as well as the external gastricenvironment most likely matched the internal concentration of nitrogensuch that there was no (or an insignificant) diffusion gradient for thenitrogen gas.

TABLE 5a Gas % v/v, by MS Detection Limit Nitrogen 64.04 0.01 Oxygen7.63 0.01 Argon 0.60 0.01 Carbon Dioxide 19.63 0.01 Hydrogen 8.10 0.01Helium not detected 0.01 Methane not detected 0.01

TABLE 5b Gas % v/v, by MS Detection Limit Nitrogen 62.33 0.01 Oxygen9.27 0.01 Argon 0.7 0.01 Carbon Dioxide 26.57 0.01 Hydrogen 1.13 0.01Helium not detected 0.01 Methane not detected 0.01

The data show that when it is desirable to minimize volume gain over theuseful life of the device, a non-barrier composite wall material may bemore desirable than a barrier wall. This observation is contrary toconventional wisdom that seeks to maintain the initial fill of gas inthe balloon by maximizing barrier properties of the intragastric balloonwall.

Simulated Gastric Environment

Balloons constructed with non-barrier film composite walls were tested(multi-layer Nylon 12/LLDPE+LDPE) in a simulated gastric environment(tank containing a 1.2 pH HCl solution with NaCl and pepsin at 40° C.with a variable N₂/CO₂ headspace; samples were taken at peak CO₂ at 50%and trough CO₂ at 0% in the tank). The balloons were initially filledwith either pure N₂ or a mixture of N₂ (75%) and CO₂ (25%), andpressure, volume, and gas gain were monitored over time. The balloonfilled with pure nitrogen exhibited significantly higher gain of CO₂when compared to the balloon filled with the N₂/CO₂ mixture. When avolume gain (as manifested in a gain of CO₂ gas) is desired, purenitrogen as the initial fill gas in connection with a non-barrier filmis desirable. Data for the experiments is provided in Table 6.

TABLE 6 Pressure Volume Volume Volume Pressure (Day) (Day) (Day) (Day)(Day) End of Cycle Balloon % CO % CO Expt. Material Sample Internal GasT = T = T = T = T = # OGB # # N or N/CO (psi) (cc) (cc) (cc) (psi) Non-N 1.12 304 312 314 1.84 Barrier 1.12 300 310 313 1.81 Film 1.09 294 309311 1.79 1.10 300 312 314 1.82 1.10 309 317 320 1.68 avg. . . B N/CO1.10 318 328 326 1.15 B (%/%) 1.00 295 301 299 1.04 B 1.10 292 300 2951.18 B 1.08 294 306 303 1.22 B 1.07 293 300 293 1.18 avg. . . VolumeVolume Pressure (Day): (Day ): (Day ): (Day ): (Day ): AM am PM PM PMEnd of Cycle % Gas % Gas Balloon Gain % CO % CO % CO Gain Expt. MaterialSample Internal Gas T = T = T = T = T = # OGB # # N or N/CO (%) (cc)(cc) (psi) (%) Non- N 7.4% 323 319 2.50 12.3% Barrier 8.2% 319 314 2.5312.3% Film 9.5% 321 313 2.56 14.1% 8.6% 324 318 2.70 14.3% 6.9% 329 3282.58 13.9% avg. .% . .% B N/CO 2.1% 329 324 1.37  2.6% B (%/%) 1.2% 302297 1.28  1.8% B 1.1% 299 293 1.25  1.0% B 2.9% 305 302 1.16  2.4% B0.5% 298 295 1.26  1.4% avg. .% . .% Volume Pressure Volume Pressure(Day ): (Day ): (Day ): (Day ): (Day ): AM AM AM PM PM End of Cycle %Gas % CO % CO % CO % CO Gain* T = T = Expt. Sample Balloon T = T = T =(cc) (psi) # Material # Internal Gas (cc) (psi) (%) balloon cut duringtest Non- N 323 3.03 16.0% Barrier 320 3.01 16.3% 318 2.84 Film 322 3.0418.7% 321 2.87 322 3.19 17.7% 322 2.98 330 3.12 17.0% 329 2.89 avg. . .%. B N/CO 329 1.82  5.7% 329 1.48 B (%/%) 300 1.61  4.0% 301 1.38 B 2991.64  4.2% 298 1.46 B 304 1.55  4.6% 306 1.33 B 299 1.62  4.0% 298 1.41avg. . .% . Volume Pressure CO % Volume (Day ): (Day ): (Day ): (Day):(Day): PM AM AM AM PM End of Cycle % Gas % Gas Gain % CO % CO Gain* % COT = T = T = T = T = Expt, Sample Balloon (%) (cc) (psi) (%) (CC) #Material # Internal Gas balloon cut during test Non- N 14.9% 322 3.0216.8% 319 Barrier 17.7% 322 3.05 18.8% 320 Film 16.7% 325 3.15 18.3% 32315.6% 331 3.08 17.0% 329 avg. .% . .% B N/CO  4.2% 327 1.63  4.4% 326 B(%/%)  3.2% 300 1.57  3.8% 299 B  3.1% 299 1.61  4.0% 296 B  4.1% 3031.45  3.9% 303 B  2.8% 300 1.60  4.1% 297 avg. .% . .% Pressure CO %Volume Pressure CO % (Day ): (Day ): (Day ): (Day ): (Day ): PM PM AM AMAM End of Cycle % Gas % CO Gain T = T = T = T = Expt. Sample Balloon T =(%) (cc) (psi) (%) # Material # Internal Gas balloon cut during testNon- N 2.90 15.5% 322 3.01 16.8% Barrier 2.92 17.7% 323 2.99 18.8% Film2.91 16.7% 325 3.07 17.9% 2.88 15.6% 332 3.03 17.1% avg. . .% . .% BN/CO 1.42  3.3% 329 1.43  4.0% B (%/%) 1.37  2.7% 301 1.42  3.4% B 1.37 2.3% 299 1.29  2.6% B 1.23  2.9% 306 1.32  4.0% B 1.42  2.6% 299 1.43 3.1% avg. . .% . .% Volume Pressure CO % Volume Pressure (Day ): (Day): (Day ): (Day ): (Day ): PM PM PM AM AM End of Cycle % Gas % CO % COGain % CO % CO T = T = T = T = T = Expt. Sample Balloon (cc) (psi) (%)(cc) (psi) # Material # Internal Gas balloon cut during test Non- N 3182.88 15.1% 323 2.96 Barrier 322 2.87 17.9% 323 3.00 Film 325 2.96 17.4%323 3.01 330 2.88 15.8% 332 2.91 avg. . .% . B N/CO 325 1.30  2.5% 3271.28 B (%/%) 314 1.28  5.8% 301 1.35 B 300 1.32  3.0% 298 1.45 B 3041.23  3.2% 307 1.35 B 299 1.34  2.7% 299 1.39 avg. . .% . CO % VolumePressure CO % Volume (Day ): (Day): (Day ): (Day ): (Day): AM AM AM AMAM End of Cycle % Gas Gain* % CO T = T = T = T = T = Expt. SampleBalloon (%) (cc) (psi) (%) (cc) # Material # Internal Gas balloon cutduring test Non- N 16.8% 323 3.00 17.0% 325 Barrier 18.8% 322 3.25 19.7%326 Film 17.1% 325 3.27 18.8% 327 16.5% 330 3.25 17.6% 333 avg. .% . .%B N/CO  2.9% 326 1.62  4.2% 330 B (%/%)  3.1% 302 1.62  4.5% 304 B  3.1%298 1.42  3.0% 300 B  4.4% 305 1.66  5.3% 309 B  3.0% 298 1.58  3.6% 298avg. .% . .% Pressure CO % Volume Pressure CO % (Day ): (Day ): (Day ):(Day): (Day ): AM AM AM AM AM End of Cycle % Gas % Gas % CO Gain* % CO %CO Gain* Expt. Sample Balloon T = T = T = T = T = # Material # InternalGas (psi) (%) (cc) (psi) (%) Non- N 3.37 19.2% 323 3.25 18.1% Barrier3.36 21.2% 327 3.21 20.7% Film 3.38 19.8% 326 3.36 19.5% 3.30 18.5% 3343.30 18.8% avg. . .% . .% B N/CO 1.68  5.3% 329 1.68  5.1% B (%/%) 1.69 5.3% 302 1.48  3.9% B 1.56  4.1% 299 1.43  3.3% B 1.69  6.3% 307 1.57 5.3% B 1.70  4.1% 300 1.66  4.4% avg. . .% . .%

Balloons constructed with various composite walls, a barrier materialNylon12/PvDC/Nylon12/LLDPE+LDPE) and a non-barrier material (multi-layerNylon12/LLDPE+LDPE) were tested in a simulated gastric environment (tankcontaining a 1.2 pH HCl solution with NaCl and pepsin at 40° C. with avariable N₂/CO₂ headspace (75%/25% to 100%/0%)). The balloons wereinitially filled with a mixture of N₂ (75%) and CO₂ (25%). Pressure forthe balloons fabricated from CO₂ barrier materials maintained pressureand volume over the time period tested, whereas the balloons fabricatedfrom CO₂ non-barrier materials exhibited substantial pressure gain overthe same time period, with a smaller volume gain. Results are presentedin Table 7.

TABLE 7 Balloon Volume Pressure Volume Pressure Internal (Day) (Day)(Day) (Day) Exp. Material Sample Gas (cc) (psi) (cc) (psi) Barrier N/CO280 1.05 (%/%) 279 1.03 avg. . Barrier N/CO 279 1.06 (%/%) 278 1.07 avg.. Barrier N/CO 280 1.05 (%/%) 278 1.02 avg. . Barrier N/CO 296 1.14(%/%) 295 1.05 avg. . Non- N/CO 304 1.12 Barrier (%/%) 292 1.11 avg. .Non- N/CO 298 1.15 Barrier (%/%) 294 1.14 avg. . Non- N/CO 297 1.14Barrier (%/%) 302 1.15 avg. . Barrier N/CO 298 1.11 (%/%) 302 1.12 avg.. Barrier N/CO 294 1.18 (%/%) 291 1.13 avg. . Barrier N/CO 286 1.05(%/%) 284 1.01 avg. . Barrier N/CO 283 0.97 (%/%) 282 1.04 avg. .Barrier N/CO 287 1.05 (%/%) 280 0.97 avg. . Barrier N/CO 303 1.28 (%/%)303 1.18 avg. . Non- N/CO 313 2.26 Barrier (%/%) 312 2.37 avg. . Non-N/CO 308 2.34 Barrier (%/%) 301 2.15 avg. . Non- N/CO 307 2.17 Barrier(%/%) 312 2.22 avg. . Barrier N/CO 303 1.28 (%/%) 303 1.28 avg. .Barrier N/CO 301 1.24 (%/%) 298 1.24 avg. . Barrier N/CO 289 1.08 2921.07 (%/%) 287 1.03 292 1.04 avg. . . Barrier N/CO 284 1.14 287 1.01(%/%) 286 1.13 287 1.02 avg. . . Barrier N/CO 285 1.09 287 1.05 (%/%)285 1.05 286 1.00 avg. . . Barrier N/CO 308 1.35 309 1.36 (%/%) 306 1.39306 1.29 avg. . . Non- N/CO 320 2.44 322 2.51 Barrier (%/%) 315 2.59 3152.58 avg. . . Non- N/CO 311 2.48 312 2.59 Barrier (%/%) 306 2.39 3082.51 avg. . . Non- N/CO 310 2.43 308 2.45 Barrier (%/%) 315 2.43 3162.54 avg. . . Barrier N/CO 305 1.39 305 1.36 (%/%) 303 1.34 306 1.31avg. . . Barrier N/CO 303 1.30 304 1.29 (%/%) 298 1.35 299 1.33 avg. . .

Balloons constructed with composite walls with high CO₂ barrierproperties (Experiments 1, 2, and 3) (Nylon12/PvDC/Nylon 12/LLDPE+LDPE)and walls having a higher permeability to CO₂ (Experiments 4, 5, and 6)consisting of multi-layer Nylon12/LLDPE+LDPE were exposed to astimulated gastric environment. The simulated gastric environmentcomprised a tank containing a 1.2 pH HCl solution with NaCl and pepsinat 40° C. The headspace in the tank was cycled from a gas mixturecomprising 75% N₂/25% CO₂ headspace to one comprising 100% N₂/0% CO₂.The balloons were initially filled with various mixtures of N₂ and CO₂,and volume was monitored. Data regarding volume changes are provided inTable 8. The balloons constructed using walls having a higherpermeability to CO₂ gained substantially in volume compared to thosewith high CO₂ barrier properties. For the balloons constructed usingwalls having a higher permeability to CO₂, those with higher ratios ofN₂ to CO₂ as initial fill gas gained less volume than those with lowerratios of N₂ to CO₂. The data demonstrate that permeation of CO₂ intoballoons fabricated with walls having a higher permeability to CO₂occurs quickly in the gastric environment, and that this process can beemployed to assist with inflation in the early stages of implant.

TABLE 8 Volume Pressure Volume Pressure Balloon (Day): (Day): (Day):(Day): Experi- Mate- Sam- Internal PM PM AM AM ment rial ple Gas (cc)(psi) (cc) (psi) Barrier N/CO 298 1.07 301 1.08 (%/%) 293 1.02 293 1.06285 1.00 . avg. . . Barrier N/CO 286 1.09 287 1.09 (%/%) 291 1.09 2941.14 293 1.08 . avg. . . Barrier N/CO 290 1.10 295 1.15 (%/%) 290 1.02290 1.03 299 1.16 304 1.20 avg. . . Non- N/CO 290 1.04 298 1.54 Barrier(%/%) 292 1.07 300 1.60 291 1.09 . avg. . . Non- N/CO 283 1.07 293 1.64Barrier (%/%) 287 1.05 295 1.60 290 1.00 300 1.48 avg. . . Non- N/CO 2871.06 297 1.76 Barrier (%/%) 298 1.07 307 1.66 290 1.13 304 1.78 avg. . .Barrier N/CO 301 1.11 301 1.13 (%/%) 295 1.06 302 1.10 284 1.03 289 1.07avg. . . Barrier N/CO 287 1.13 287 1.12 (%/%) 294 1.13 296 1.17 297 1.15300 1.19 avg. . . Barrier N/CO 294 1.17 297 1.21 (%/%) 290 1.08 294 1.10302 1.27 308 1.27 avg. . . Non- N/CO 296 1.48 297 1.72 Barrier (%/%) 2981.55 302 1.81 296 1.65 301 1.80 avg. . . Non- N/CO 291 1.56 294 1.80Barrier (%/%) 295 1.50 295 1.67 298 1.44 301 1.65 avg. . . Non- N/CO 2951.76 300 1.99 Barrier (%/%)

Human Gastric Environment

Balloons constructed with non-barrier film composite walls were testedin vivo in 10 patients in a clinical study for 30 days. The balloon wallcomprised multi-layer Nylon 12/LLDPE+LDPE. One balloon per patient wasadministered. Balloons were filled with a mixed gas to approximately 245cc with an average starting balloon pressure of 1.01 psi aboveatmosphere. The initial fill gas was 95% Nitrogen and 5% CO₂. At the endof 30 days, balloons remained full and firm, although ending pressureand volumes could not be discerned visually/endoscopically. Of the 10balloons retrieved, 10 balloons had internal gas samples obtained, and 8provided meaningful data. Table 9 provides the data retrieved from theballoons. The end gas samples are reflective of the gastric environmentand are averaged as follows: 82.4% N₂, 10.6% O₂, 5.9% CO₂, and 0.84% Ar.Thus, the internal balloon environment reflects that of the averagegastric environment gas concentrations. Data for the experiments isprovided in Table 9.

TABLE 9 Starting Balloon Ending Balloon Gas Gas Concentration Patient #Concentration (% v/v, by MS) Patient # N] CO] N] O] CO] Ar] 1 95.00 5.0081.19 10.20 7.60 0.86 2 95.00 5.00 81.24 12.90 4.85 0.86 3 95.00 5.0082.41 10.80 5.65 0.85 4 95.00 5.00 82.07 11.20 5.70 0.82 5 95.00 5.0082.87 10.05 6.00 0.82 6 95.00 5.00 82.54 11.50 4.80 0.88 7 95.00 5.00Erroneous Sample 8 95.00 5.00 81.76 10.20 7.00 0.82 9 95.00 5.00Erroneous Sample 10 95.00 5.00 84.95 8.20 5.80 0.81 Avg. . . . . Std Dev. . . . Max . . . . Min . . . .

In certain embodiments wherein it is desirable to maintain the startingpressure and volume of the device, this can be accomplished by matchingthe internal balloon environment at implant (i.e., the fill gases)closely to the gastric environment. In such embodiments, the balloon canbe inflated with an initial gas fill gas comprising approximately 80-85%nitrogen, 8-12% oxygen, and 4-8% carbon dioxide. The concentration ofargon and other in vivo gases can be considered inconsequential to thetotal volume/pressure, and may be omitted for convenience or included asdesirable. To encourage inflation of the balloon in vivo, the startingconcentrations of oxygen and/or carbon dioxide can be reduced.

The present invention has been described above with reference tospecific embodiments. However, other embodiments than the abovedescribed are equally possible within the scope of the invention.Different method steps than those described above may be provided withinthe scope of the invention. The different features and steps of theinvention may be combined in other combinations than those described.The scope of the invention is only limited by the appended patentclaims.

All references cited herein are incorporated herein by reference intheir entirety. To the extent publications and patents or patentapplications incorporated by reference contradict the disclosurecontained in the specification, the specification is intended tosupersede and/or take precedence over any such contradictory material.

To the extent publications and patents or patent applicationsincorporated by reference herein contradict the disclosure contained inthe specification, the specification is intended to supersede and/ortake precedence over any such contradictory material.

Unless otherwise defined, all terms (including technical and scientificterms) are to be given their ordinary and customary meaning to a personof ordinary skill in the art, and are not to be limited to a special orcustomized meaning unless expressly so defined herein.

Terms and phrases used in this application, and variations thereof,unless otherwise expressly stated, should be construed as open ended asopposed to limiting. As examples of the foregoing, the term ‘including’should be read to mean ‘including, without limitation’ or the like; theterm ‘comprising’ as used herein is synonymous with ‘including,’‘containing,’ or ‘characterized by,’ and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps; theterm ‘example’ is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; adjectives suchas ‘known’, ‘normal’, ‘standard’, and terms of similar meaning shouldnot be construed as limiting the item described to a given time periodor to an item available as of a given time, but instead should be readto encompass known, normal, or standard technologies that may beavailable or known now or at any time in the future; and use of termslike ‘preferably,’ preferred, ‘desired,’ or ‘desirable,’ and words ofsimilar meaning should not be understood as implying that certainfeatures are critical, essential, or even important to the structure orfunction of the invention, but instead as merely intended to highlightalternative or additional features that may or may not be utilized in aparticular embodiment of the invention. Likewise, a group of itemslinked with the conjunction ‘and’ should not be read as requiring thateach and every one of those items be present in the grouping, but rathershould be read as ‘and/or’ unless expressly stated otherwise. Similarly,a group of items linked with the conjunction ‘or’ should not be read asrequiring mutual exclusivity among that group, but rather should be readas ‘and/or’ unless expressly stated otherwise. In addition, as used inthis application, the articles ‘a’ and ‘an’ should be construed asreferring to one or more than one (i.e., to at least one) of thegrammatical objects of the article. By way of example, ‘an element’means one element or more than one element.

The presence in some instances of broadening words and phrases such as‘one or more’, ‘at least’, ‘but not limited to’, or other like phrasesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent.

All numbers expressing quantities of ingredients, reaction conditions,and so forth used in the specification are to be understood as beingmodified in all instances by the term ‘about.’ Accordingly, unlessindicated to the contrary, the numerical parameters set forth herein areapproximations that may vary depending upon the desired propertiessought to be obtained. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of anyclaims in any application claiming priority to the present application,each numerical parameter should be construed in light of the number ofsignificant digits and ordinary rounding approaches.

Furthermore, although the foregoing has been described in some detail byway of illustrations and examples for purposes of clarity andunderstanding, it is apparent to those skilled in the art that certainchanges and modifications may be practiced. Therefore, the descriptionand examples should not be construed as limiting the scope of theinvention to the specific embodiments and examples described herein, butrather to also cover all modification and alternatives coming with thetrue scope and spirit of the invention.

What is claimed is:
 1. An intragastric balloon configured to have auseful life in an in vivo gastric environment of at least 30 days,comprising: a polymeric wall configured to have, under conditions of anin vivo gastric environment, a permeability to CO₂ of more than 10cc/m²/day, such that a rate and an amount of diffusion of CO₂ from thein vivo gastric environment into a lumen of the balloon through thepolymeric wall is controlled, at least in part, by a concentration of aninert gas in an initial fill gas, wherein the polymeric wall comprisesone or more expandable sections configured to stretch from 10% to 400%in response to an increased volume of a fluid inside thevolume-occupying subcomponent; and a valve system configured forintroducing the initial fill gas into the lumen of the balloon in the invivo gastric environment.
 2. The intragastric balloon of claim 1,wherein the polymeric wall comprises a three layer CO₂ barrier materialconsisting of nylon/polyvinylidene chloride/polyethylene.
 3. Theintragastric balloon of claim 1, wherein the polymeric wall comprises atwo layer CO₂ barrier material consisting of nylon/polyethylene materialand no additional CO₂ barrier material.
 4. The intragastric balloon ofclaim 1, wherein the initial fill gas consists essentially of SF₆ andN₂.
 5. The intragastric balloon of claim 1, wherein the initial fill gasconsists essentially of SF₆.
 6. The intragastric balloon of claim 1,wherein an entirety of the polymeric wall is expandable.
 7. Theintragastric balloon of claim 1, comprising one or more non-expandablesections.
 8. The intragastric balloon of claim 1, wherein the one ormore expandable sections comprises a band positioned around any sectionof the intragastric balloon.
 9. The intragastric balloon of claim 8,wherein the band wraps around a circumference of the intragastricballoon.
 10. The intragastric balloon of claim 8, wherein the band hasone or more curved or angled sections.
 11. The intragastric balloon ofclaim 1, wherein the one or more expandable sections comprises multiplebands of expandable material.
 12. The intragastric balloon of claim 1,comprising one or more non-expandable bands positioned around anysection of the intragastric balloon.
 13. The intragastric balloon ofclaim 1, comprising a plurality of expandable panels.
 14. Theintragastric balloon of claim 13, wherein the expandable panels are eachthe same size.
 15. The intragastric balloon of claim 13, comprising aplurality of nonexpandable panels.
 16. The intragastric balloon of claim15, wherein the nonexpandable panels comprise a mesh.
 17. Theintragastric balloon of claim 15, wherein there are an equal number ofexpandable panels and nonexpandable panels.
 18. The intragastric balloonof claim 1, comprising one or more expandable protrusions configured toprotrude from a surface of the intragastric balloon.
 19. Theintragastric balloon of claim 1, wherein the polymeric wall comprises aplurality of layers, wherein one or more sections of the layers areexpandable.
 20. A method for inflating an intragastric balloon,comprising: introducing, in an in vivo intragastric environment, aninitial fill gas comprising an inert gas into a lumen of an intragastricballoon according to claim 1; and exposing the balloon to the in vivointragastric environment for a useful life of at least 30 days, whereina rate and an amount of diffusion of CO₂ from the in vivo gastricenvironment into the lumen of the balloon through the polymeric wall iscontrolled, at least in part, by a concentration of an inert gas in theinitial fill gas.